[libcxx-commits] [libcxx] 59f266d - [chrono][test] Fixes some tests on Windows.

Mark de Wever via libcxx-commits libcxx-commits at lists.llvm.org
Tue Jun 20 10:35:43 PDT 2023


Author: Mark de Wever
Date: 2023-06-20T19:35:38+02:00
New Revision: 59f266d2e2789256f7e8a584fcdc159b357f114a

URL: https://github.com/llvm/llvm-project/commit/59f266d2e2789256f7e8a584fcdc159b357f114a
DIFF: https://github.com/llvm/llvm-project/commit/59f266d2e2789256f7e8a584fcdc159b357f114a.diff

LOG: [chrono][test] Fixes some tests on Windows.

The tests switched from assert to TEST_EQUAL to make it easier to debug
assertion failures. This is used to fix most tests on Windows.

Some CI tests give no output, which needs to be investigated separately.

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D152062

Added: 
    

Modified: 
    libcxx/test/std/time/time.cal/time.cal.md/time.cal.md.nonmembers/ostream.pass.cpp
    libcxx/test/std/time/time.cal/time.cal.mdlast/ostream.pass.cpp
    libcxx/test/std/time/time.cal/time.cal.month/time.cal.month.nonmembers/ostream.pass.cpp
    libcxx/test/std/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/ostream.pass.cpp
    libcxx/test/std/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/ostream.pass.cpp
    libcxx/test/std/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/ostream.pass.cpp
    libcxx/test/std/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/ostream.pass.cpp
    libcxx/test/std/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/ostream.pass.cpp
    libcxx/test/std/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/ostream.pass.cpp
    libcxx/test/std/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/ostream.pass.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/test/std/time/time.cal/time.cal.md/time.cal.md.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.md/time.cal.md.nonmembers/ostream.pass.cpp
index b70b687e8731f..681d97ee2695a 100644
--- a/libcxx/test/std/time/time.cal/time.cal.md/time.cal.md.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.md/time.cal.md.nonmembers/ostream.pass.cpp
@@ -10,9 +10,6 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
@@ -33,9 +30,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::month_day md) {
   std::basic_stringstream<CharT> sstr;
@@ -65,63 +69,70 @@ template <class CharT>
 static void test() {
   using namespace std::literals::chrono_literals;
 
-  assert(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 0d}) ==
-         SV("0 is not a valid month/00 is not a valid day"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 1d}) == SV("0 is not a valid month/01"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}) ==
-         SV("Jan/255 is not a valid day"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}) == SV("Jan/31"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 0d}),
+             SV("0 is not a valid month/00 is not a valid day"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 1d}),
+             SV("0 is not a valid month/01"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}),
+             SV("Jan/255 is not a valid day"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}), SV("Jan/31"));
   // February is considered valid with 29 days; it lacks the year information
   // to do a proper validation.
-  assert(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}) == SV("Feb/29"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}), SV("Feb/29"));
   // The month_day stream operator has no validation, this means never validate
   // dates don't get
   //   Jun/31 is not a valid month day
   // which is inconsistent with other stream operators.
   // TODO FMT file an issue about this.
-  assert(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}) == SV("Jun/31"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}), SV("Jun/31"));
 
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 0d}) ==
-         SV("0 is not a valid month/00 is not a valid day"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 1d}) ==
-         SV("0 is not a valid month/01"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 0d}),
+             SV("0 is not a valid month/00 is not a valid day"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 1d}),
+             SV("0 is not a valid month/01"));
 #if defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}) ==
-         SV("jan/255 is not a valid day"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}) == SV("jan/31"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}) == SV("fév/29"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}) == SV("jui/31"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}),
+             SV("jan/255 is not a valid day"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}), SV("jan/31"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}), SV("fév/29"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}), SV("jui/31"));
 #else  //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}) ==
-         SV("janv./255 is not a valid day"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}) == SV("janv./31"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}) == SV("févr./29"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}) == SV("juin/31"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}),
+             SV("janv./255 is not a valid day"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}), SV("janv./31"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}), SV("févr./29"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}), SV("juin/31"));
 #endif //  defined(__APPLE__)
 
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 0d}) ==
-         SV("0 is not a valid month/00 is not a valid day"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 1d}) ==
-         SV("0 is not a valid month/01"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 0d}),
+             SV("0 is not a valid month/00 is not a valid day"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{0}, 1d}),
+             SV("0 is not a valid month/01"));
 #if defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}) ==
-         SV(" 1/255 is not a valid day"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}) == SV(" 1/31"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}) == SV(" 2/29"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}) == SV(" 6/31"));
-#elif defined(_AIX) || defined(_WIN32) //  defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}) ==
-         SV("1月/255 is not a valid day"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}) == SV("1月/31"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}) == SV("2月/29"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}) == SV("6月/31"));
-#else                                  //  defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}) ==
-         SV(" 1月/255 is not a valid day"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}) == SV(" 1月/31"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}) == SV(" 2月/29"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}) == SV(" 6月/31"));
-#endif                                 //  defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}),
+             SV(" 1/255 is not a valid day"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}), SV(" 1/31"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}), SV(" 2/29"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}), SV(" 6/31"));
+#elif defined(_WIN32) //  defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}),
+             SV("1/255 is not a valid day"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}), SV("1/31"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}), SV("2/29"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}), SV("6/31"));
+#elif defined(_AIX)   //  defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}),
+             SV("1月/255 is not a valid day"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}), SV("1月/31"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}), SV("2月/29"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}), SV("6月/31"));
+#else                 //  defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 255d}),
+             SV(" 1月/255 is not a valid day"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{1}, 31d}), SV(" 1月/31"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{2}, 29d}), SV(" 2月/29"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day{std::chrono::month{6}, 31d}), SV(" 6月/31"));
+#endif                //  defined(__APPLE__)
 }
 
 int main(int, char**) {

diff  --git a/libcxx/test/std/time/time.cal/time.cal.mdlast/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.mdlast/ostream.pass.cpp
index 92ecff1f5bc56..9dc8e1ef10c68 100644
--- a/libcxx/test/std/time/time.cal/time.cal.mdlast/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.mdlast/ostream.pass.cpp
@@ -12,9 +12,6 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
@@ -36,9 +33,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::month_day_last mdl) {
   std::basic_stringstream<CharT> sstr;
@@ -66,108 +70,120 @@ static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::month_day_last
 
 template <class CharT>
 static void test() {
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{0}}) ==
-         SV("0 is not a valid month/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}) == SV("Jan/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}) == SV("Feb/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}) == SV("Mar/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}) == SV("Apr/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}) == SV("May/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}) == SV("Jun/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}) == SV("Jul/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}) == SV("Aug/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}) == SV("Sep/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}) == SV("Oct/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}) == SV("Nov/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}) == SV("Dec/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{13}}) ==
-         SV("13 is not a valid month/last"));
-  assert(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{255}}) ==
-         SV("255 is not a valid month/last"));
-
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{0}}) ==
-         SV("0 is not a valid month/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{0}}),
+             SV("0 is not a valid month/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}), SV("Jan/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}), SV("Feb/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}), SV("Mar/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}), SV("Apr/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}), SV("May/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}), SV("Jun/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}), SV("Jul/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}), SV("Aug/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}), SV("Sep/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}), SV("Oct/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}), SV("Nov/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}), SV("Dec/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{13}}),
+             SV("13 is not a valid month/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_day_last{std::chrono::month{255}}),
+             SV("255 is not a valid month/last"));
+
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{0}}),
+             SV("0 is not a valid month/last"));
 #if defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}) == SV("jan/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}) == SV("fév/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}) == SV("mar/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}) == SV("avr/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}) == SV("mai/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}) == SV("jui/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}) == SV("jul/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}) == SV("aoû/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}) == SV("sep/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}) == SV("oct/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}) == SV("nov/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}) == SV("déc/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}), SV("jan/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}), SV("fév/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}), SV("mar/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}), SV("avr/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}), SV("mai/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}), SV("jui/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}), SV("jul/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}), SV("aoû/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}), SV("sep/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}), SV("oct/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}), SV("nov/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}), SV("déc/last"));
 #else //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}) == SV("janv./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}) == SV("févr./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}) == SV("mars/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}), SV("janv./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}), SV("févr./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}), SV("mars/last"));
 #  if defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}) == SV("avr./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}), SV("avr./last"));
 #  else
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}) == SV("avril/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}), SV("avril/last"));
 #  endif
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}) == SV("mai/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}) == SV("juin/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}) == SV("juil./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}) == SV("août/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}) == SV("sept./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}) == SV("oct./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}) == SV("nov./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}) == SV("déc./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}), SV("mai/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}), SV("juin/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}), SV("juil./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}), SV("août/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}), SV("sept./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}), SV("oct./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}), SV("nov./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}), SV("déc./last"));
 #endif //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{13}}) ==
-         SV("13 is not a valid month/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{255}}) ==
-         SV("255 is not a valid month/last"));
-
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{0}}) ==
-         SV("0 is not a valid month/last"));
-#if defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}) == SV(" 1/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}) == SV(" 2/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}) == SV(" 3/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}) == SV(" 4/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}) == SV(" 5/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}) == SV(" 6/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}) == SV(" 7/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}) == SV(" 8/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}) == SV(" 9/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}) == SV("10/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}) == SV("11/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}) == SV("12/last"));
-#else    // defined(__APPLE__)
-#  if defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}) == SV("1月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}) == SV("2月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}) == SV("3月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}) == SV("4月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}) == SV("5月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}) == SV("6月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}) == SV("7月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}) == SV("8月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}) == SV("9月/last"));
-#  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}) == SV(" 1月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}) == SV(" 2月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}) == SV(" 3月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}) == SV(" 4月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}) == SV(" 5月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}) == SV(" 6月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}) == SV(" 7月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}) == SV(" 8月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}) == SV(" 9月/last"));
-#  endif // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}) == SV("10月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}) == SV("11月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}) == SV("12月/last"));
-#endif   // defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{13}}) ==
-         SV("13 is not a valid month/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{255}}) ==
-         SV("255 is not a valid month/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{13}}),
+             SV("13 is not a valid month/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_day_last{std::chrono::month{255}}),
+             SV("255 is not a valid month/last"));
+
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{0}}),
+             SV("0 is not a valid month/last"));
+#if defined(__APPLE__) || defined(_WIN32)
+#  if defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}), SV(" 1/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}), SV(" 2/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}), SV(" 3/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}), SV(" 4/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}), SV(" 5/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}), SV(" 6/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}), SV(" 7/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}), SV(" 8/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}), SV(" 9/last"));
+#  else  // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}), SV("1/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}), SV("2/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}), SV("3/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}), SV("4/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}), SV("5/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}), SV("6/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}), SV("7/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}), SV("8/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}), SV("9/last"));
+#  endif // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}), SV("10/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}), SV("11/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}), SV("12/last"));
+#else // defined(__APPLE__) || defined(_WIN32)
+#  if defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}), SV("1月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}), SV("2月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}), SV("3月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}), SV("4月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}), SV("5月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}), SV("6月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}), SV("7月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}), SV("8月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}), SV("9月/last"));
+#  else  // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{1}}), SV(" 1月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{2}}), SV(" 2月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{3}}), SV(" 3月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{4}}), SV(" 4月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{5}}), SV(" 5月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{6}}), SV(" 6月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{7}}), SV(" 7月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{8}}), SV(" 8月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{9}}), SV(" 9月/last"));
+#  endif // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{10}}), SV("10月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{11}}), SV("11月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{12}}), SV("12月/last"));
+#endif   // defined(__APPLE__) || defined(_WIN32)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{13}}),
+             SV("13 is not a valid month/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_day_last{std::chrono::month{255}}),
+             SV("255 is not a valid month/last"));
 }
 
 int main(int, char**) {

diff  --git a/libcxx/test/std/time/time.cal/time.cal.month/time.cal.month.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.month/time.cal.month.nonmembers/ostream.pass.cpp
index f2e2301888fe9..7833a1612cace 100644
--- a/libcxx/test/std/time/time.cal/time.cal.month/time.cal.month.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.month/time.cal.month.nonmembers/ostream.pass.cpp
@@ -12,9 +12,6 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
@@ -36,9 +33,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::month month) {
   std::basic_stringstream<CharT> sstr;
@@ -66,99 +70,111 @@ static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::month month) {
 
 template <class CharT>
 static void test() {
-  assert(stream_c_locale<CharT>(std::chrono::month{0}) == SV("0 is not a valid month"));
-  assert(stream_c_locale<CharT>(std::chrono::month{1}) == SV("Jan"));
-  assert(stream_c_locale<CharT>(std::chrono::month{2}) == SV("Feb"));
-  assert(stream_c_locale<CharT>(std::chrono::month{3}) == SV("Mar"));
-  assert(stream_c_locale<CharT>(std::chrono::month{4}) == SV("Apr"));
-  assert(stream_c_locale<CharT>(std::chrono::month{5}) == SV("May"));
-  assert(stream_c_locale<CharT>(std::chrono::month{6}) == SV("Jun"));
-  assert(stream_c_locale<CharT>(std::chrono::month{7}) == SV("Jul"));
-  assert(stream_c_locale<CharT>(std::chrono::month{8}) == SV("Aug"));
-  assert(stream_c_locale<CharT>(std::chrono::month{9}) == SV("Sep"));
-  assert(stream_c_locale<CharT>(std::chrono::month{10}) == SV("Oct"));
-  assert(stream_c_locale<CharT>(std::chrono::month{11}) == SV("Nov"));
-  assert(stream_c_locale<CharT>(std::chrono::month{12}) == SV("Dec"));
-  assert(stream_c_locale<CharT>(std::chrono::month{13}) == SV("13 is not a valid month"));
-  assert(stream_c_locale<CharT>(std::chrono::month{255}) == SV("255 is not a valid month"));
-
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{0}) == SV("0 is not a valid month"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{0}), SV("0 is not a valid month"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{1}), SV("Jan"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{2}), SV("Feb"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{3}), SV("Mar"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{4}), SV("Apr"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{5}), SV("May"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{6}), SV("Jun"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{7}), SV("Jul"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{8}), SV("Aug"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{9}), SV("Sep"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{10}), SV("Oct"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{11}), SV("Nov"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{12}), SV("Dec"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{13}), SV("13 is not a valid month"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month{255}), SV("255 is not a valid month"));
+
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{0}), SV("0 is not a valid month"));
 #if defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{1}) == SV("jan"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{2}) == SV("fév"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{3}) == SV("mar"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{4}) == SV("avr"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{5}) == SV("mai"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{6}) == SV("jui"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{7}) == SV("jul"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{8}) == SV("aoû"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{9}) == SV("sep"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{10}) == SV("oct"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{11}) == SV("nov"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{12}) == SV("déc"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{1}), SV("jan"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{2}), SV("fév"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{3}), SV("mar"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{4}), SV("avr"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{5}), SV("mai"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{6}), SV("jui"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{7}), SV("jul"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{8}), SV("aoû"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{9}), SV("sep"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{10}), SV("oct"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{11}), SV("nov"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{12}), SV("déc"));
 #else //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{1}) == SV("janv."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{2}) == SV("févr."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{3}) == SV("mars"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{1}), SV("janv."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{2}), SV("févr."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{3}), SV("mars"));
 #  if defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{4}) == SV("avr."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{4}), SV("avr."));
 #  else
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{4}) == SV("avril"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{4}), SV("avril"));
 #  endif
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{5}) == SV("mai"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{6}) == SV("juin"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{7}) == SV("juil."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{8}) == SV("août"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{9}) == SV("sept."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{10}) == SV("oct."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{11}) == SV("nov."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{12}) == SV("déc."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{5}), SV("mai"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{6}), SV("juin"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{7}), SV("juil."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{8}), SV("août"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{9}), SV("sept."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{10}), SV("oct."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{11}), SV("nov."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{12}), SV("déc."));
 #endif //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{13}) == SV("13 is not a valid month"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month{255}) == SV("255 is not a valid month"));
-
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{0}) == SV("0 is not a valid month"));
-#if defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{1}) == SV(" 1"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{2}) == SV(" 2"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{3}) == SV(" 3"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{4}) == SV(" 4"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{5}) == SV(" 5"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{6}) == SV(" 6"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{7}) == SV(" 7"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{8}) == SV(" 8"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{9}) == SV(" 9"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{10}) == SV("10"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{11}) == SV("11"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{12}) == SV("12"));
-#else // defined(__APPLE__)
-#  if defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{1}) == SV("1月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{2}) == SV("2月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{3}) == SV("3月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{4}) == SV("4月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{5}) == SV("5月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{6}) == SV("6月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{7}) == SV("7月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{8}) == SV("8月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{9}) == SV("9月"));
-#  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{1}) == SV(" 1月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{2}) == SV(" 2月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{3}) == SV(" 3月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{4}) == SV(" 4月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{5}) == SV(" 5月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{6}) == SV(" 6月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{7}) == SV(" 7月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{8}) == SV(" 8月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{9}) == SV(" 9月"));
-#  endif // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{10}) == SV("10月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{11}) == SV("11月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{12}) == SV("12月"));
-#endif   // defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{13}) == SV("13 is not a valid month"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month{255}) == SV("255 is not a valid month"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{13}), SV("13 is not a valid month"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month{255}), SV("255 is not a valid month"));
+
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{0}), SV("0 is not a valid month"));
+#if defined(__APPLE__) || defined(_WIN32)
+#  if defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{1}), SV(" 1"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{2}), SV(" 2"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{3}), SV(" 3"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{4}), SV(" 4"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{5}), SV(" 5"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{6}), SV(" 6"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{7}), SV(" 7"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{8}), SV(" 8"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{9}), SV(" 9"));
+#  else  //  defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{1}), SV("1"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{2}), SV("2"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{3}), SV("3"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{4}), SV("4"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{5}), SV("5"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{6}), SV("6"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{7}), SV("7"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{8}), SV("8"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{9}), SV("9"));
+#  endif // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{10}), SV("10"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{11}), SV("11"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{12}), SV("12"));
+#else // defined(__APPLE__)|| defined(_WIN32)
+#  if defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{1}), SV("1月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{2}), SV("2月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{3}), SV("3月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{4}), SV("4月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{5}), SV("5月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{6}), SV("6月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{7}), SV("7月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{8}), SV("8月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{9}), SV("9月"));
+#  else  // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{1}), SV(" 1月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{2}), SV(" 2月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{3}), SV(" 3月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{4}), SV(" 4月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{5}), SV(" 5月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{6}), SV(" 6月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{7}), SV(" 7月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{8}), SV(" 8月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{9}), SV(" 9月"));
+#  endif // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{10}), SV("10月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{11}), SV("11月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{12}), SV("12月"));
+#endif   // defined(__APPLE__)|| defined(_WIN32)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{13}), SV("13 is not a valid month"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month{255}), SV("255 is not a valid month"));
 }
 
 int main(int, char**) {

diff  --git a/libcxx/test/std/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/ostream.pass.cpp
index c86bbbbb6c7fd..9fffad9224f9c 100644
--- a/libcxx/test/std/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/ostream.pass.cpp
@@ -12,9 +12,6 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
@@ -36,9 +33,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::month_weekday mwd) {
   std::basic_stringstream<CharT> sstr;
@@ -66,214 +70,296 @@ static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::month_weekday m
 
 template <class CharT>
 static void test() {
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) ==
-         SV("0 is not a valid month/Sun[1]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}) == SV("Jan/Mon[1]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}) == SV("Feb/Tue[2]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}) == SV("Mar/Wed[3]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}) == SV("Apr/Thu[4]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}) == SV("May/Fri[5]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}) ==
-         SV("Jun/Sat[6 is not a valid index]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}) ==
-         SV("Jul/Sun[7 is not a valid index]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV("Aug/8 is not a valid weekday[0 is not a valid index]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("Sep/Sun[1]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("Oct/Sun[1]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("Nov/Sun[1]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("Dec/Sun[1]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{13}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) ==
-         SV("13 is not a valid month/Sun[1]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{255}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV("255 is not a valid month/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("0 is not a valid month/Sun[1]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}),
+             SV("Jan/Mon[1]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}),
+             SV("Feb/Tue[2]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}),
+             SV("Mar/Wed[3]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}),
+             SV("Apr/Thu[4]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}),
+             SV("May/Fri[5]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}),
+             SV("Jun/Sat[6 is not a valid index]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}),
+             SV("Jul/Sun[7 is not a valid index]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV("Aug/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("Sep/Sun[1]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("Oct/Sun[1]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("Nov/Sun[1]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("Dec/Sun[1]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{13}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("13 is not a valid month/Sun[1]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{255}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV("255 is not a valid month/8 is not a valid weekday[0 is not a valid index]"));
 
 #if defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) ==
-         SV("0 is not a valid month/Dim[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}) == SV("jan/Lun[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}) == SV("fév/Mar[2]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}) == SV("mar/Mer[3]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}) == SV("avr/Jeu[4]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}) == SV("mai/Ven[5]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}) ==
-         SV("jui/Sam[6 is not a valid index]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}) ==
-         SV("jul/Dim[7 is not a valid index]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV("aoû/8 is not a valid weekday[0 is not a valid index]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("sep/Dim[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("oct/Dim[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("nov/Dim[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("déc/Dim[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{13}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) ==
-         SV("13 is not a valid month/Dim[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{255}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV("255 is not a valid month/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("0 is not a valid month/Dim[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}),
+             SV("jan/Lun[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}),
+             SV("fév/Mar[2]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}),
+             SV("mar/Mer[3]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}),
+             SV("avr/Jeu[4]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}),
+             SV("mai/Ven[5]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}),
+             SV("jui/Sam[6 is not a valid index]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}),
+             SV("jul/Dim[7 is not a valid index]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV("aoû/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("sep/Dim[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("oct/Dim[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("nov/Dim[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("déc/Dim[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{13}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("13 is not a valid month/Dim[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{255}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV("255 is not a valid month/8 is not a valid weekday[0 is not a valid index]"));
 #else //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) ==
-         SV("0 is not a valid month/dim.[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}) == SV("janv./lun.[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}) == SV("févr./mar.[2]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}) == SV("mars/mer.[3]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("0 is not a valid month/dim.[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}),
+             SV("janv./lun.[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}),
+             SV("févr./mar.[2]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}),
+             SV("mars/mer.[3]"));
 #  if defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}) == SV("avr./jeu.[4]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}),
+             SV("avr./jeu.[4]"));
 #  else
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}) == SV("avril/jeu.[4]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}),
+             SV("avril/jeu.[4]"));
 #  endif
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}) == SV("mai/ven.[5]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}) ==
-         SV("juin/sam.[6 is not a valid index]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}) ==
-         SV("juil./dim.[7 is not a valid index]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV("août/8 is not a valid weekday[0 is not a valid index]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("sept./dim.[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("oct./dim.[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("nov./dim.[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("déc./dim.[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{13}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) ==
-         SV("13 is not a valid month/dim.[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{255}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV("255 is not a valid month/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}),
+             SV("mai/ven.[5]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}),
+             SV("juin/sam.[6 is not a valid index]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}),
+             SV("juil./dim.[7 is not a valid index]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV("août/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("sept./dim.[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("oct./dim.[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("nov./dim.[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("déc./dim.[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{13}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("13 is not a valid month/dim.[1]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{255}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV("255 is not a valid month/8 is not a valid weekday[0 is not a valid index]"));
 #endif //  defined(__APPLE__)
 
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) ==
-         SV("0 is not a valid month/日[1]"));
-#if defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}) == SV(" 1/月[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}) == SV(" 2/火[2]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}) == SV(" 3/水[3]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}) == SV(" 4/木[4]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}) == SV(" 5/金[5]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}) ==
-         SV(" 6/土[6 is not a valid index]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}) ==
-         SV(" 7/日[7 is not a valid index]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV(" 8/8 is not a valid weekday[0 is not a valid index]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV(" 9/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("10/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("11/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("12/日[1]"));
-#else    // defined(__APPLE__)
-#  if defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}) == SV("1月/月[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}) == SV("2月/火[2]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}) == SV("3月/水[3]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}) == SV("4月/木[4]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}) == SV("5月/金[5]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}) ==
-         SV("6月/土[6 is not a valid index]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}) ==
-         SV("7月/日[7 is not a valid index]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV("8月/8 is not a valid weekday[0 is not a valid index]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("9月/日[1]"));
-#  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}) == SV(" 1月/月[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}) == SV(" 2月/火[2]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}) == SV(" 3月/水[3]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}) == SV(" 4月/木[4]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}) == SV(" 5月/金[5]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}) ==
-         SV(" 6月/土[6 is not a valid index]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}) ==
-         SV(" 7月/日[7 is not a valid index]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV(" 8月/8 is not a valid weekday[0 is not a valid index]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV(" 9月/日[1]"));
-#  endif // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("10月/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("11月/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) == SV("12月/日[1]"));
-#endif   // defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{13}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}) ==
-         SV("13 is not a valid month/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
-             std::chrono::month{255}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}) ==
-         SV("255 is not a valid month/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("0 is not a valid month/日[1]"));
+#if defined(__APPLE__) || defined(_WIN32)
+#  if defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}),
+             SV(" 1/月[1]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}),
+             SV(" 2/火[2]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}),
+             SV(" 3/水[3]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}),
+             SV(" 4/木[4]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}),
+             SV(" 5/金[5]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}),
+             SV(" 6/土[6 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}),
+             SV(" 7/日[7 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV(" 8/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV(" 9/日[1]"));
+#  else  // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}),
+             SV("1/月[1]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}),
+             SV("2/火[2]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}),
+             SV("3/水[3]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}),
+             SV("4/木[4]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}),
+             SV("5/金[5]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}),
+             SV("6/土[6 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}),
+             SV("7/日[7 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV("8/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("9/日[1]"));
+#  endif // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("10/日[1]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("11/日[1]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("12/日[1]"));
+#else // defined(__APPLE__) || defined(_WIN32)
+#  if defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}),
+             SV("1月/月[1]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}),
+             SV("2月/火[2]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}),
+             SV("3月/水[3]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}),
+             SV("4月/木[4]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}),
+             SV("5月/金[5]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}),
+             SV("6月/土[6 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}),
+             SV("7月/日[7 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV("8月/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("9月/日[1]"));
+#  else  // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday{1}, 1}}),
+             SV(" 1月/月[1]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{2}, std::chrono::weekday_indexed{std::chrono::weekday{2}, 2}}),
+             SV(" 2月/火[2]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{3}, std::chrono::weekday_indexed{std::chrono::weekday{3}, 3}}),
+             SV(" 3月/水[3]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{4}, std::chrono::weekday_indexed{std::chrono::weekday{4}, 4}}),
+             SV(" 4月/木[4]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{5}, std::chrono::weekday_indexed{std::chrono::weekday{5}, 5}}),
+             SV(" 5月/金[5]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{6}, std::chrono::weekday_indexed{std::chrono::weekday{6}, 6}}),
+             SV(" 6月/土[6 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{7}, std::chrono::weekday_indexed{std::chrono::weekday{7}, 7}}),
+             SV(" 7月/日[7 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{8}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV(" 8月/8 is not a valid weekday[0 is not a valid index]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{9}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV(" 9月/日[1]"));
+#  endif // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{10}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("10月/日[1]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{11}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("11月/日[1]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{12}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("12月/日[1]"));
+#endif   // defined(__APPLE__) || defined(_WIN32)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{13}, std::chrono::weekday_indexed{std::chrono::weekday{0}, 1}}),
+             SV("13 is not a valid month/日[1]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday{
+                 std::chrono::month{255}, std::chrono::weekday_indexed{std::chrono::weekday{8}, 0}}),
+             SV("255 is not a valid month/8 is not a valid weekday[0 is not a valid index]"));
 }
 
 int main(int, char**) {

diff  --git a/libcxx/test/std/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/ostream.pass.cpp
index 4f20478c871b2..ee75fd208c4cc 100644
--- a/libcxx/test/std/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/ostream.pass.cpp
@@ -12,9 +12,6 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
@@ -36,9 +33,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::month_weekday_last mwdl) {
   std::basic_stringstream<CharT> sstr;
@@ -66,205 +70,299 @@ static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::month_weekday_l
 
 template <class CharT>
 static void test() {
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("0 is not a valid month/Sun[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("Jan/Sun[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}) == SV("Feb/Mon[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}) == SV("Mar/Tue[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}) == SV("Apr/Wed[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}) == SV("May/Thu[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}) == SV("Jun/Fri[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}) == SV("Jul/Sat[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}) == SV("Aug/Sun[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("Sep/8 is not a valid weekday[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("Oct/Sun[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("Nov/Sun[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("Dec/Sun[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{13}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("13 is not a valid month/Sun[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{255}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("255 is not a valid month/8 is not a valid weekday[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("0 is not a valid month/Sun[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("Jan/Sun[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}),
+             SV("Feb/Mon[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}),
+             SV("Mar/Tue[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}),
+             SV("Apr/Wed[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}),
+             SV("May/Thu[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}),
+             SV("Jun/Fri[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}),
+             SV("Jul/Sat[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}),
+             SV("Aug/Sun[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV("Sep/8 is not a valid weekday[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("Oct/Sun[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("Nov/Sun[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("Dec/Sun[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{13}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("13 is not a valid month/Sun[last]"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{255}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV("255 is not a valid month/8 is not a valid weekday[last]"));
 
 #if defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("0 is not a valid month/Dim[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("jan/Dim[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}) == SV("fév/Lun[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}) == SV("mar/Mar[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}) == SV("avr/Mer[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}) == SV("mai/Jeu[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}) == SV("jui/Ven[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}) == SV("jul/Sam[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}) == SV("aoû/Dim[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("sep/8 is not a valid weekday[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("oct/Dim[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("nov/Dim[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("déc/Dim[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{13}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("13 is not a valid month/Dim[last]"));
-#else    //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("0 is not a valid month/dim.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("janv./dim.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}) == SV("févr./lun.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}) == SV("mars/mar.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("0 is not a valid month/Dim[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("jan/Dim[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}),
+             SV("fév/Lun[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}),
+             SV("mar/Mar[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}),
+             SV("avr/Mer[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}),
+             SV("mai/Jeu[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}),
+             SV("jui/Ven[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}),
+             SV("jul/Sam[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}),
+             SV("aoû/Dim[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV("sep/8 is not a valid weekday[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("oct/Dim[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("nov/Dim[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("déc/Dim[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{13}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("13 is not a valid month/Dim[last]"));
+#else //  defined(__APPLE__)
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("0 is not a valid month/dim.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("janv./dim.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}),
+             SV("févr./lun.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}),
+             SV("mars/mar.[last]"));
 #  if defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}) == SV("avr./mer.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}),
+             SV("avr./mer.[last]"));
 #  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}) == SV("avril/mer.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}),
+             SV("avril/mer.[last]"));
 #  endif // defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}) == SV("mai/jeu.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}) == SV("juin/ven.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}) == SV("juil./sam.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}) == SV("août/dim.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("sept./8 is not a valid weekday[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("oct./dim.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("nov./dim.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("déc./dim.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{13}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("13 is not a valid month/dim.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}),
+             SV("mai/jeu.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}),
+             SV("juin/ven.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}),
+             SV("juil./sam.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}),
+             SV("août/dim.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV("sept./8 is not a valid weekday[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("oct./dim.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("nov./dim.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("déc./dim.[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{13}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("13 is not a valid month/dim.[last]"));
 #endif   //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{255}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("255 is not a valid month/8 is not a valid weekday[last]"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{255}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV("255 is not a valid month/8 is not a valid weekday[last]"));
 
-#if defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("0 is not a valid month/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV(" 1/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}) == SV(" 2/月[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}) == SV(" 3/火[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}) == SV(" 4/水[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}) == SV(" 5/木[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}) == SV(" 6/金[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}) == SV(" 7/土[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}) == SV(" 8/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV(" 9/8 is not a valid weekday[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("10/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("11/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("12/日[last]"));
-#else    // defined(__APPLE__)
-#  if defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("0 is not a valid month/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("1月/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}) == SV("2月/月[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}) == SV("3月/火[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}) == SV("4月/水[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}) == SV("5月/木[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}) == SV("6月/金[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}) == SV("7月/土[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}) == SV("8月/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("9月/8 is not a valid weekday[last]"));
-#  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("0 is not a valid month/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV(" 1月/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}) == SV(" 2月/月[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}) == SV(" 3月/火[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}) == SV(" 4月/水[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}) == SV(" 5月/木[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}) == SV(" 6月/金[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}) == SV(" 7月/土[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}) == SV(" 8月/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV(" 9月/8 is not a valid weekday[last]"));
-#  endif // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("10月/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("11月/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}) == SV("12月/日[last]"));
-#endif   // defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{13}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("13 is not a valid month/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
-             std::chrono::month{255}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("255 is not a valid month/8 is not a valid weekday[last]"));
+#if defined(__APPLE__) || defined(_WIN32)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("0 is not a valid month/日[last]"));
+#  if defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV(" 1/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}),
+             SV(" 2/月[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}),
+             SV(" 3/火[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}),
+             SV(" 4/水[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}),
+             SV(" 5/木[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}),
+             SV(" 6/金[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}),
+             SV(" 7/土[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}),
+             SV(" 8/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV(" 9/8 is not a valid weekday[last]"));
+#  else  // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("1/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}),
+             SV("2/月[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}),
+             SV("3/火[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}),
+             SV("4/水[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}),
+             SV("5/木[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}),
+             SV("6/金[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}),
+             SV("7/土[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}),
+             SV("8/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV("9/8 is not a valid weekday[last]"));
+#  endif // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("10/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("11/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("12/日[last]"));
+#else // defined(__APPLE__) || defined(_WIN32)
+#  if defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("0 is not a valid month/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("1月/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}),
+             SV("2月/月[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}),
+             SV("3月/火[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}),
+             SV("4月/水[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}),
+             SV("5月/木[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}),
+             SV("6月/金[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}),
+             SV("7月/土[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}),
+             SV("8月/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV("9月/8 is not a valid weekday[last]"));
+#  else  // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("0 is not a valid month/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV(" 1月/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{2}, std::chrono::weekday_last{std::chrono::weekday{1}}}),
+             SV(" 2月/月[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{3}, std::chrono::weekday_last{std::chrono::weekday{2}}}),
+             SV(" 3月/火[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{4}, std::chrono::weekday_last{std::chrono::weekday{3}}}),
+             SV(" 4月/水[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{5}, std::chrono::weekday_last{std::chrono::weekday{4}}}),
+             SV(" 5月/木[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{6}, std::chrono::weekday_last{std::chrono::weekday{5}}}),
+             SV(" 6月/金[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{7}, std::chrono::weekday_last{std::chrono::weekday{6}}}),
+             SV(" 7月/土[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{8}, std::chrono::weekday_last{std::chrono::weekday{7}}}),
+             SV(" 8月/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{9}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV(" 9月/8 is not a valid weekday[last]"));
+#  endif // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{10}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("10月/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{11}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("11月/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{12}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("12月/日[last]"));
+#endif   // defined(__APPLE__) || defined(_WIN32)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{13}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("13 is not a valid month/日[last]"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::month_weekday_last{
+                 std::chrono::month{255}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+             SV("255 is not a valid month/8 is not a valid weekday[last]"));
 }
 
 int main(int, char**) {

diff  --git a/libcxx/test/std/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/ostream.pass.cpp
index b1fffbffffec5..0955ba11d6078 100644
--- a/libcxx/test/std/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/ostream.pass.cpp
@@ -12,9 +12,6 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
@@ -36,9 +33,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::year_month ym) {
   std::basic_stringstream<CharT> sstr;
@@ -66,178 +70,199 @@ static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::year_month ym)
 
 template <class CharT>
 static void test() {
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{0}}) ==
-         SV("-32768 is not a valid year/0 is not a valid month"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}) ==
-         SV("-32768 is not a valid year/Jan"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}) ==
-         SV("-32767/Feb"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}) ==
-         SV("0000/Mar"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}) ==
-         SV("1970/Apr"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}) ==
-         SV("32767/May"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}) ==
-         SV("0000/Jun"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}) ==
-         SV("0000/Jul"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}) ==
-         SV("0000/Aug"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}) ==
-         SV("0000/Sep"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}) ==
-         SV("0000/Oct"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}) ==
-         SV("0000/Nov"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}) ==
-         SV("0000/Dec"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{13}}) ==
-         SV("0000/13 is not a valid month"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{255}}) ==
-         SV("-32768 is not a valid year/255 is not a valid month"));
-
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{0}}) ==
-         SV("-32768 is not a valid year/0 is not a valid month"));
-#if defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}) ==
-         SV("-32768 is not a valid year/jan"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}) ==
-         SV("-32767/fév"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}) ==
-         SV("0000/mar"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}) ==
-         SV("1970/avr"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}) ==
-         SV("32767/mai"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}) ==
-         SV("0000/jui"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}) ==
-         SV("0000/jul"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}) ==
-         SV("0000/aoû"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}) ==
-         SV("0000/sep"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}) ==
-         SV("0000/oct"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}) ==
-         SV("0000/nov"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}) ==
-         SV("0000/déc"));
-#else    //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}) ==
-         SV("-32768 is not a valid year/janv."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}) ==
-         SV("-32767/févr."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}) ==
-         SV("0000/mars"));
-#  if defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}) ==
-         SV("1970/avr."));
-#  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}) ==
-         SV("1970/avril"));
-#  endif // defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}) ==
-         SV("32767/mai"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}) ==
-         SV("0000/juin"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}) ==
-         SV("0000/juil."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}) ==
-         SV("0000/août"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}) ==
-         SV("0000/sept."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}) ==
-         SV("0000/oct."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}) ==
-         SV("0000/nov."));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}) ==
-         SV("0000/déc."));
-#endif   //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{13}}) ==
-         SV("0000/13 is not a valid month"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{255}}) ==
-         SV("-32768 is not a valid year/255 is not a valid month"));
-
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{0}}) ==
-         SV("-32768 is not a valid year/0 is not a valid month"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{0}}),
+             SV("-32768 is not a valid year/0 is not a valid month"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}),
+             SV("-32768 is not a valid year/Jan"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}),
+             SV("-32767/Feb"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}),
+             SV("0000/Mar"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}),
+             SV("1970/Apr"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}),
+             SV("32767/May"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}),
+             SV("0000/Jun"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}),
+             SV("0000/Jul"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}),
+             SV("0000/Aug"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}),
+             SV("0000/Sep"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}),
+             SV("0000/Oct"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}),
+             SV("0000/Nov"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}),
+             SV("0000/Dec"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{13}}),
+             SV("0000/13 is not a valid month"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{255}}),
+             SV("-32768 is not a valid year/255 is not a valid month"));
+
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{0}}),
+             SV("-32768 is not a valid year/0 is not a valid month"));
 #if defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}) ==
-         SV("-32768 is not a valid year/ 1"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}) ==
-         SV("-32767/ 2"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}) ==
-         SV("0000/ 3"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}) ==
-         SV("1970/ 4"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}) ==
-         SV("32767/ 5"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}) ==
-         SV("0000/ 6"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}) ==
-         SV("0000/ 7"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}) ==
-         SV("0000/ 8"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}) ==
-         SV("0000/ 9"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}) ==
-         SV("0000/10"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}) ==
-         SV("0000/11"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}) ==
-         SV("0000/12"));
-#else    // defined(__APPLE__)
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}),
+             SV("-32768 is not a valid year/jan"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}),
+             SV("-32767/fév"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}),
+             SV("0000/mar"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}),
+             SV("1970/avr"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}),
+             SV("32767/mai"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}),
+             SV("0000/jui"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}),
+             SV("0000/jul"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}),
+             SV("0000/aoû"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}),
+             SV("0000/sep"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}),
+             SV("0000/oct"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}),
+             SV("0000/nov"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}),
+             SV("0000/déc"));
+#else //  defined(__APPLE__)
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}),
+             SV("-32768 is not a valid year/janv."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}),
+             SV("-32767/févr."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}),
+             SV("0000/mars"));
 #  if defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}) ==
-         SV("-32768 is not a valid year/1月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}) ==
-         SV("-32767/2月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}) ==
-         SV("0000/3月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}) ==
-         SV("1970/4月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}) ==
-         SV("32767/5月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}) ==
-         SV("0000/6月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}) ==
-         SV("0000/7月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}) ==
-         SV("0000/8月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}) ==
-         SV("0000/9月"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}),
+             SV("1970/avr."));
 #  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}) ==
-         SV("-32768 is not a valid year/ 1月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}) ==
-         SV("-32767/ 2月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}) ==
-         SV("0000/ 3月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}) ==
-         SV("1970/ 4月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}) ==
-         SV("32767/ 5月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}) ==
-         SV("0000/ 6月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}) ==
-         SV("0000/ 7月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}) ==
-         SV("0000/ 8月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}) ==
-         SV("0000/ 9月"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}),
+             SV("1970/avril"));
 #  endif // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}) ==
-         SV("0000/10月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}) ==
-         SV("0000/11月"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}) ==
-         SV("0000/12月"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}),
+             SV("32767/mai"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}),
+             SV("0000/juin"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}),
+             SV("0000/juil."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}),
+             SV("0000/août"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}),
+             SV("0000/sept."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}),
+             SV("0000/oct."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}),
+             SV("0000/nov."));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}),
+             SV("0000/déc."));
 #endif   // defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{13}}) ==
-         SV("0000/13 is not a valid month"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{255}}) ==
-         SV("-32768 is not a valid year/255 is not a valid month"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{13}}),
+             SV("0000/13 is not a valid month"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{255}}),
+             SV("-32768 is not a valid year/255 is not a valid month"));
+
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{0}}),
+             SV("-32768 is not a valid year/0 is not a valid month"));
+#if defined(__APPLE__) || defined(_WIN32)
+#  if defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}),
+             SV("-32768 is not a valid year/ 1"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}),
+             SV("-32767/ 2"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}),
+             SV("0000/ 3"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}),
+             SV("1970/ 4"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}),
+             SV("32767/ 5"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}),
+             SV("0000/ 6"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}),
+             SV("0000/ 7"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}),
+             SV("0000/ 8"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}),
+             SV("0000/ 9"));
+#  else  // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}),
+             SV("-32768 is not a valid year/1"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}),
+             SV("-32767/2"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}),
+             SV("0000/3"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}),
+             SV("1970/4"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}),
+             SV("32767/5"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}),
+             SV("0000/6"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}),
+             SV("0000/7"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}),
+             SV("0000/8"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}),
+             SV("0000/9"));
+#  endif // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}),
+             SV("0000/10"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}),
+             SV("0000/11"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}),
+             SV("0000/12"));
+#else // defined(__APPLE__) || defined(_WIN32)
+#  if defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}),
+             SV("-32768 is not a valid year/1月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}),
+             SV("-32767/2月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}),
+             SV("0000/3月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}),
+             SV("1970/4月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}),
+             SV("32767/5月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}),
+             SV("0000/6月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}),
+             SV("0000/7月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}),
+             SV("0000/8月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}),
+             SV("0000/9月"));
+#  else  // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{1}}),
+             SV("-32768 is not a valid year/ 1月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'767}, std::chrono::month{2}}),
+             SV("-32767/ 2月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{3}}),
+             SV("0000/ 3月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{1970}, std::chrono::month{4}}),
+             SV("1970/ 4月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{32'767}, std::chrono::month{5}}),
+             SV("32767/ 5月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{6}}),
+             SV("0000/ 6月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{7}}),
+             SV("0000/ 7月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{8}}),
+             SV("0000/ 8月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{9}}),
+             SV("0000/ 9月"));
+#  endif // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{10}}),
+             SV("0000/10月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{11}}),
+             SV("0000/11月"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{12}}),
+             SV("0000/12月"));
+#endif   // defined(__APPLE__) || defined(_WIN32)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{0}, std::chrono::month{13}}),
+             SV("0000/13 is not a valid month"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month{std::chrono::year{-32'768}, std::chrono::month{255}}),
+             SV("-32768 is not a valid year/255 is not a valid month"));
 }
 
 int main(int, char**) {

diff  --git a/libcxx/test/std/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/ostream.pass.cpp
index c2810da515805..ffc737fcad5dd 100644
--- a/libcxx/test/std/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/ostream.pass.cpp
@@ -10,12 +10,12 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
+// TODO FMT Investigate Windows issues.
+// XFAIL: msvc
+
 // REQUIRES: locale.fr_FR.UTF-8
 // REQUIRES: locale.ja_JP.UTF-8
 
@@ -34,9 +34,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::year_month_day ymd) {
   std::basic_stringstream<CharT> sstr;
@@ -64,78 +71,102 @@ static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::year_month_day
 
 template <class CharT>
 static void test() {
-  assert(stream_c_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::day{1}}) ==
-         SV("-32768-01-01 is not a valid date"));
-  assert(stream_c_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::day{1}}) ==
-         SV("-32767-00-01 is not a valid date"));
-  assert(stream_c_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::day{0}}) ==
-         SV("-32767-01-00 is not a valid date"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{1970}, std::chrono::month{1}, std::chrono::day{1}}) == SV("1970-01-01"));
-  assert(stream_c_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{1999}, std::chrono::month{2}, std::chrono::day{29}}) ==
-         SV("1999-02-29 is not a valid date"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{2000}, std::chrono::month{2}, std::chrono::day{29}}) == SV("2000-02-29"));
+  TEST_EQUAL(stream_c_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::day{1}}),
+             SV("-32768-01-01 is not a valid date"));
+  TEST_EQUAL(stream_c_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::day{1}}),
+             SV("-32767-00-01 is not a valid date"));
+  TEST_EQUAL(stream_c_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::day{0}}),
+             SV("-32767-01-00 is not a valid date"));
+  TEST_EQUAL(stream_c_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{1970}, std::chrono::month{1}, std::chrono::day{1}}),
+             SV("1970-01-01"));
+  TEST_EQUAL(stream_c_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{1999}, std::chrono::month{2}, std::chrono::day{29}}),
+             SV("1999-02-29 is not a valid date"));
+  TEST_EQUAL(stream_c_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{2000}, std::chrono::month{2}, std::chrono::day{29}}),
+             SV("2000-02-29"));
 
 #if defined(_AIX)
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}) == SV("+32767-12-31"));
-#else  // defined(_AIX)
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}) == SV("32767-12-31"));
-#endif // defined(_AIX)
-
-  assert(stream_fr_FR_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::day{1}}) ==
-         SV("-32768-01-01 is not a valid date"));
-  assert(stream_fr_FR_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::day{1}}) ==
-         SV("-32767-00-01 is not a valid date"));
-  assert(stream_fr_FR_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::day{0}}) ==
-         SV("-32767-01-00 is not a valid date"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{1970}, std::chrono::month{1}, std::chrono::day{1}}) == SV("1970-01-01"));
-  assert(stream_fr_FR_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{1999}, std::chrono::month{2}, std::chrono::day{29}}) ==
-         SV("1999-02-29 is not a valid date"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{2000}, std::chrono::month{2}, std::chrono::day{29}}) == SV("2000-02-29"));
+  TEST_EQUAL(stream_c_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}),
+             SV("+32767-12-31"));
+#elif defined(_WIN32) // defined(_AIX)
+  TEST_EQUAL(stream_c_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}),
+             SV(""));
+#else                 //  defined(_AIX)
+  TEST_EQUAL(stream_c_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}),
+             SV("32767-12-31"));
+#endif                // defined(_AIX)
+
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::day{1}}),
+             SV("-32768-01-01 is not a valid date"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::day{1}}),
+             SV("-32767-00-01 is not a valid date"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::day{0}}),
+             SV("-32767-01-00 is not a valid date"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{1970}, std::chrono::month{1}, std::chrono::day{1}}),
+             SV("1970-01-01"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{1999}, std::chrono::month{2}, std::chrono::day{29}}),
+             SV("1999-02-29 is not a valid date"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{2000}, std::chrono::month{2}, std::chrono::day{29}}),
+             SV("2000-02-29"));
 #if defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}) == SV("+32767-12-31"));
-#else  // defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}) == SV("32767-12-31"));
-#endif // defined(_AIX)
-
-  assert(stream_ja_JP_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::day{1}}) ==
-         SV("-32768-01-01 is not a valid date"));
-  assert(stream_ja_JP_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::day{1}}) ==
-         SV("-32767-00-01 is not a valid date"));
-  assert(stream_ja_JP_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::day{0}}) ==
-         SV("-32767-01-00 is not a valid date"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{1970}, std::chrono::month{1}, std::chrono::day{1}}) == SV("1970-01-01"));
-  assert(stream_ja_JP_locale<CharT>(
-             std::chrono::year_month_day{std::chrono::year{1999}, std::chrono::month{2}, std::chrono::day{29}}) ==
-         SV("1999-02-29 is not a valid date"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{2000}, std::chrono::month{2}, std::chrono::day{29}}) == SV("2000-02-29"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}),
+             SV("+32767-12-31"));
+#elif defined(_WIN32) // defined(_AIX)
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}),
+             SV(""));
+#else                 // defined(_AIX)
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}),
+             SV("32767-12-31"));
+#endif                // defined(_AIX)
+
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::day{1}}),
+             SV("-32768-01-01 is not a valid date"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::day{1}}),
+             SV("-32767-00-01 is not a valid date"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::day{0}}),
+             SV("-32767-01-00 is not a valid date"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{1970}, std::chrono::month{1}, std::chrono::day{1}}),
+             SV("1970-01-01"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{1999}, std::chrono::month{2}, std::chrono::day{29}}),
+             SV("1999-02-29 is not a valid date"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{2000}, std::chrono::month{2}, std::chrono::day{29}}),
+             SV("2000-02-29"));
 #if defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}) == SV("+32767-12-31"));
-#else  // defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day{
-             std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}) == SV("32767-12-31"));
-#endif // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}),
+             SV("+32767-12-31"));
+#elif defined(_WIN32) // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}),
+             SV(""));
+#else                 // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                 std::chrono::year_month_day{std::chrono::year{32'767}, std::chrono::month{12}, std::chrono::day{31}}),
+             SV("32767-12-31"));
+#endif                // defined(_AIX)
 }
 
 int main(int, char**) {

diff  --git a/libcxx/test/std/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/ostream.pass.cpp
index 533eee454bf00..933edaab75b0d 100644
--- a/libcxx/test/std/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/ostream.pass.cpp
@@ -12,9 +12,6 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
@@ -36,9 +33,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::year_month_day_last ymdl) {
   std::basic_stringstream<CharT> sstr;
@@ -66,195 +70,287 @@ static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::year_month_day_
 
 template <class CharT>
 static void test() {
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{0}}}) ==
-         SV("0000/0 is not a valid month/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}) ==
-         SV("-32768 is not a valid year/Jan/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}) == SV("-32767/Feb/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}) == SV("0000/Mar/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}) == SV("1970/Apr/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}) == SV("32767/May/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}) == SV("0000/Jun/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}) == SV("0000/Jul/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}) == SV("0000/Aug/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}) == SV("0000/Sep/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}) == SV("0000/Oct/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}) == SV("0000/Nov/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}) == SV("0000/Dec/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{13}}}) ==
-         SV("0000/13 is not a valid month/last"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{255}}}) ==
-         SV("-32768 is not a valid year/255 is not a valid month/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{0}}}),
+             SV("0000/0 is not a valid month/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}),
+             SV("-32768 is not a valid year/Jan/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}),
+             SV("-32767/Feb/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}),
+             SV("0000/Mar/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}),
+             SV("1970/Apr/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}),
+             SV("32767/May/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}),
+             SV("0000/Jun/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}),
+             SV("0000/Jul/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}),
+             SV("0000/Aug/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}),
+             SV("0000/Sep/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}),
+             SV("0000/Oct/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}),
+             SV("0000/Nov/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}),
+             SV("0000/Dec/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{13}}}),
+             SV("0000/13 is not a valid month/last"));
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{255}}}),
+             SV("-32768 is not a valid year/255 is not a valid month/last"));
 
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{0}}}) ==
-         SV("0000/0 is not a valid month/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{0}}}),
+             SV("0000/0 is not a valid month/last"));
 #if defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}) ==
-         SV("-32768 is not a valid year/jan/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}) == SV("-32767/fév/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}) == SV("0000/mar/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}) == SV("1970/avr/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}) == SV("32767/mai/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}) == SV("0000/jui/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}) == SV("0000/jul/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}) == SV("0000/aoû/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}) == SV("0000/sep/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}) == SV("0000/oct/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}) == SV("0000/nov/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}) == SV("0000/déc/last"));
-#else    //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}) ==
-         SV("-32768 is not a valid year/janv./last"));
-  assert(
-      stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-          std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}) == SV("-32767/févr./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}) == SV("0000/mars/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}),
+             SV("-32768 is not a valid year/jan/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}),
+             SV("-32767/fév/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}),
+             SV("0000/mar/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}),
+             SV("1970/avr/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}),
+             SV("32767/mai/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}),
+             SV("0000/jui/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}),
+             SV("0000/jul/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}),
+             SV("0000/aoû/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}),
+             SV("0000/sep/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}),
+             SV("0000/oct/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}),
+             SV("0000/nov/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}),
+             SV("0000/déc/last"));
+#else //  defined(__APPLE__)
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}),
+             SV("-32768 is not a valid year/janv./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}),
+             SV("-32767/févr./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}),
+             SV("0000/mars/last"));
 #  if defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}) == SV("1970/avr./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}),
+             SV("1970/avr./last"));
 #  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}) == SV("1970/avril/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}),
+             SV("1970/avril/last"));
 #  endif // defined(_WIN32) || defined(_AIX)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}) == SV("32767/mai/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}) == SV("0000/juin/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}) == SV("0000/juil./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}) == SV("0000/août/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}) == SV("0000/sept./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}) == SV("0000/oct./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}) == SV("0000/nov./last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}) == SV("0000/déc./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}),
+             SV("32767/mai/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}),
+             SV("0000/juin/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}),
+             SV("0000/juil./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}),
+             SV("0000/août/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}),
+             SV("0000/sept./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}),
+             SV("0000/oct./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}),
+             SV("0000/nov./last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}),
+             SV("0000/déc./last"));
 #endif   //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{13}}}) ==
-         SV("0000/13 is not a valid month/last"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{255}}}) ==
-         SV("-32768 is not a valid year/255 is not a valid month/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{13}}}),
+             SV("0000/13 is not a valid month/last"));
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{255}}}),
+             SV("-32768 is not a valid year/255 is not a valid month/last"));
 
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{0}}}) ==
-         SV("0000/0 is not a valid month/last"));
-#if defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}) ==
-         SV("-32768 is not a valid year/ 1/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}) == SV("-32767/ 2/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}) == SV("0000/ 3/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}) == SV("1970/ 4/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}) == SV("32767/ 5/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}) == SV("0000/ 6/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}) == SV("0000/ 7/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}) == SV("0000/ 8/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}) == SV("0000/ 9/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}) == SV("0000/10/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}) == SV("0000/11/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}) == SV("0000/12/last"));
-#else    // defined(__APPLE__)
-#  if defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}) ==
-         SV("-32768 is not a valid year/1月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}) == SV("-32767/2月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}) == SV("0000/3月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}) == SV("1970/4月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}) == SV("32767/5月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}) == SV("0000/6月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}) == SV("0000/7月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}) == SV("0000/8月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}) == SV("0000/9月/last"));
-#  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}) ==
-         SV("-32768 is not a valid year/ 1月/last"));
-  assert(
-      stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-          std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}) == SV("-32767/ 2月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}) == SV("0000/ 3月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}) == SV("1970/ 4月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}) == SV("32767/ 5月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}) == SV("0000/ 6月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}) == SV("0000/ 7月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}) == SV("0000/ 8月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}) == SV("0000/ 9月/last"));
-#  endif // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}) == SV("0000/10月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}) == SV("0000/11月/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}) == SV("0000/12月/last"));
-#endif   // defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{13}}}) ==
-         SV("0000/13 is not a valid month/last"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
-             std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{255}}}) ==
-         SV("-32768 is not a valid year/255 is not a valid month/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{0}}}),
+             SV("0000/0 is not a valid month/last"));
+#if defined(__APPLE__) || defined(_WIN32)
+#  if defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}),
+             SV("-32768 is not a valid year/ 1/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}),
+             SV("-32767/ 2/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}),
+             SV("0000/ 3/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}),
+             SV("1970/ 4/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}),
+             SV("32767/ 5/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}),
+             SV("0000/ 6/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}),
+             SV("0000/ 7/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}),
+             SV("0000/ 8/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}),
+             SV("0000/ 9/last"));
+#  else  // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}),
+             SV("-32768 is not a valid year/1/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}),
+             SV("-32767/2/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}),
+             SV("0000/3/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}),
+             SV("1970/4/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}),
+             SV("32767/5/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}),
+             SV("0000/6/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}),
+             SV("0000/7/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}),
+             SV("0000/8/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}),
+             SV("0000/9/last"));
+#  endif // defined(__APPLE__)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}),
+             SV("0000/10/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}),
+             SV("0000/11/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}),
+             SV("0000/12/last"));
+#else // defined(__APPLE__) || defined(_WIN32)
+#  if defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}),
+             SV("-32768 is not a valid year/1月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}),
+             SV("-32767/2月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}),
+             SV("0000/3月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}),
+             SV("1970/4月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}),
+             SV("32767/5月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}),
+             SV("0000/6月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}),
+             SV("0000/7月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}),
+             SV("0000/8月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}),
+             SV("0000/9月/last"));
+#  else  // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{1}}}),
+             SV("-32768 is not a valid year/ 1月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'767}, std::chrono::month_day_last{std::chrono::month{2}}}),
+             SV("-32767/ 2月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{3}}}),
+             SV("0000/ 3月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{1970}, std::chrono::month_day_last{std::chrono::month{4}}}),
+             SV("1970/ 4月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{32'767}, std::chrono::month_day_last{std::chrono::month{5}}}),
+             SV("32767/ 5月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{6}}}),
+             SV("0000/ 6月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{7}}}),
+             SV("0000/ 7月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{8}}}),
+             SV("0000/ 8月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{9}}}),
+             SV("0000/ 9月/last"));
+#  endif // defined(_AIX)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{10}}}),
+             SV("0000/10月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{11}}}),
+             SV("0000/11月/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{12}}}),
+             SV("0000/12月/last"));
+#endif   // defined(__APPLE__) || defined(_WIN32)
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{0}, std::chrono::month_day_last{std::chrono::month{13}}}),
+             SV("0000/13 is not a valid month/last"));
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_day_last{
+                 std::chrono::year{-32'768}, std::chrono::month_day_last{std::chrono::month{255}}}),
+             SV("-32768 is not a valid year/255 is not a valid month/last"));
 }
 
 int main(int, char**) {

diff  --git a/libcxx/test/std/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/ostream.pass.cpp
index 68732be589236..d8bab676ab948 100644
--- a/libcxx/test/std/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/ostream.pass.cpp
@@ -10,9 +10,6 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
@@ -34,9 +31,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::year_month_weekday ymwd) {
   std::basic_stringstream<CharT> sstr;
@@ -64,180 +68,191 @@ static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::year_month_week
 
 template <class CharT>
 static void test() {
-  assert(stream_c_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'768},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32768 is not a valid year/Jan/Sun[1]"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{0},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/0 is not a valid month/Sun[1]"));
-  assert(
+  TEST_EQUAL(
+      stream_c_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32768 is not a valid year/Jan/Sun[1]"));
+  TEST_EQUAL(
       stream_c_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{-32'767},
-          std::chrono::month{1},
-          std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}) == SV("-32767/Jan/8 is not a valid weekday[1]"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}) ==
-         SV("-32767/Jan/Sun[0 is not a valid index]")); // note 0 is a valid index here...
-  assert(stream_c_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/Jan/Sun[1]"));
-
-  assert(
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/0 is not a valid month/Sun[1]"));
+  TEST_EQUAL(
       stream_c_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) ==
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}),
+      SV("-32767/Jan/8 is not a valid weekday[1]"));
+  TEST_EQUAL(
+      stream_c_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}),
+      SV("-32767/Jan/Sun[0 is not a valid index]")); // note 0 is a valid index here...
+  TEST_EQUAL(
+      stream_c_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/Jan/Sun[1]"));
+
+  TEST_EQUAL(
+      stream_c_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
       SV("1970/Jan/Sun[1]"));
 
 #if defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'768},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32768 is not a valid year/jan/Dim[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{0},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/0 is not a valid month/Dim[1]"));
-  assert(
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32768 is not a valid year/jan/Dim[1]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/0 is not a valid month/Dim[1]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}),
+      SV("-32767/jan/8 is not a valid weekday[1]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}),
+      SV("-32767/jan/Dim[0 is not a valid index]")); // note 0 is a valid index here...
+  TEST_EQUAL(
       stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{-32'767},
-          std::chrono::month{1},
-          std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}) == SV("-32767/jan/8 is not a valid weekday[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}) ==
-         SV("-32767/jan/Dim[0 is not a valid index]")); // note 0 is a valid index here...
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/jan/Dim[1]"));
-
-  assert(
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/jan/Dim[1]"));
+
+  TEST_EQUAL(
       stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) ==
+          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
       SV("1970/jan/Dim[1]"));
 #else  //  defined(__APPLE__)
-  assert(
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32768 is not a valid year/janv./dim.[1]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/0 is not a valid month/dim.[1]"));
+  TEST_EQUAL(
       stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{-32'768},
-          std::chrono::month{1},
-          std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32768 is not a valid year/janv./dim.[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{0},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/0 is not a valid month/dim.[1]"));
-  assert(
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}),
+      SV("-32767/janv./8 is not a valid weekday[1]"));
+  TEST_EQUAL(
       stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{-32'767},
-          std::chrono::month{1},
-          std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}) == SV("-32767/janv./8 is not a valid weekday[1]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}) ==
-         SV("-32767/janv./dim.[0 is not a valid index]")); // note 0 is a valid index here...
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/janv./dim.[1]"));
-
-  assert(
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}),
+      SV("-32767/janv./dim.[0 is not a valid index]")); // note 0 is a valid index here...
+  TEST_EQUAL(
       stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) ==
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/janv./dim.[1]"));
+
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
       SV("1970/janv./dim.[1]"));
 #endif //  defined(__APPLE__)
 
 #if defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'768},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32768 is not a valid year/ 1/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{0},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/0 is not a valid month/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}) == SV("-32767/ 1/8 is not a valid weekday[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}) ==
-         SV("-32767/ 1/日[0 is not a valid index]")); // note 0 is a valid index here...
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/ 1/日[1]"));
-
-  assert(
-      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) ==
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32768 is not a valid year/ 1/日[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/0 is not a valid month/日[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}),
+      SV("-32767/ 1/8 is not a valid weekday[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}),
+      SV("-32767/ 1/日[0 is not a valid index]")); // note 0 is a valid index here...
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/ 1/日[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
       SV("1970/ 1/日[1]"));
-#else    // defined(__APPLE__)
-#  if defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'768},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32768 is not a valid year/1月/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{0},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/0 is not a valid month/日[1]"));
-  assert(
-      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{-32'767},
-          std::chrono::month{1},
-          std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}) == SV("-32767/1月/8 is not a valid weekday[1]"));
-
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}) ==
-         SV("-32767/1月/日[0 is not a valid index]")); // note 0 is a valid index here...
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/1月/日[1]"));
-
-  assert(
-      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) ==
+#elif defined(_WIN32) // defined(__APPLE__)
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32768 is not a valid year/1/日[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/0 is not a valid month/日[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}),
+      SV("-32767/1/8 is not a valid weekday[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}),
+      SV("-32767/1/日[0 is not a valid index]")); // note 0 is a valid index here...
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/1/日[1]"));
+
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("1970/1/日[1]"));
+#elif defined(_AIX)   // defined(__APPLE__)
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32768 is not a valid year/1月/日[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/0 is not a valid month/日[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}),
+      SV("-32767/1月/8 is not a valid weekday[1]"));
+
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}),
+      SV("-32767/1月/日[0 is not a valid index]")); // note 0 is a valid index here...
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/1月/日[1]"));
+
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
       SV("1970/1月/日[1]"));
-#  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'768},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32768 is not a valid year/ 1月/日[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{0},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/0 is not a valid month/日[1]"));
-  assert(
-      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{-32'767},
-          std::chrono::month{1},
-          std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}) == SV("-32767/ 1月/8 is not a valid weekday[1]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}) ==
-         SV("-32767/ 1月/日[0 is not a valid index]")); // note 0 is a valid index here...
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-             std::chrono::year{-32'767},
-             std::chrono::month{1},
-             std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) == SV("-32767/ 1月/日[1]"));
-
-  assert(
-      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
-          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}) ==
+#else                 // defined(__APPLE__)
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32768 is not a valid year/ 1月/日[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/0 is not a valid month/日[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(8), 1}}),
+      SV("-32767/ 1月/8 is not a valid weekday[1]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 0}}),
+      SV("-32767/ 1月/日[0 is not a valid index]")); // note 0 is a valid index here...
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
+      SV("-32767/ 1月/日[1]"));
+
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday{
+          std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_indexed{std::chrono::weekday(0), 1}}),
       SV("1970/ 1月/日[1]"));
-#  endif // defined(_WIN32) || defined(_AIX)
-#endif   // defined(__APPLE__)
+#endif                // defined(__APPLE__)
 }
 
 int main(int, char**) {

diff  --git a/libcxx/test/std/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/ostream.pass.cpp
index d60caa129ed85..77161da6c407d 100644
--- a/libcxx/test/std/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/ostream.pass.cpp
@@ -10,9 +10,6 @@
 // UNSUPPORTED: no-localization
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// TODO FMT Investigate Windows issues.
-// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
-
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
@@ -34,9 +31,16 @@
 #include "make_string.h"
 #include "platform_support.h" // locale name macros
 #include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
 template <class CharT>
 static std::basic_string<CharT> stream_c_locale(std::chrono::year_month_weekday_last ymwdl) {
   std::basic_stringstream<CharT> sstr;
@@ -64,114 +68,157 @@ static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::year_month_week
 
 template <class CharT>
 static void test() {
-  assert(stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32768 is not a valid year/Jan/Sun[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/0 is not a valid month/Sun[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("-32767/Jan/8 is not a valid weekday[last]"));
-  assert(stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/Jan/Sun[last]"));
-
-  assert(stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("1970/Jan/Sun[last]"));
+  TEST_EQUAL(
+      stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32768 is not a valid year/Jan/Sun[last]"));
+  TEST_EQUAL(
+      stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/0 is not a valid month/Sun[last]"));
+  TEST_EQUAL(
+      stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+      SV("-32767/Jan/8 is not a valid weekday[last]"));
+  TEST_EQUAL(
+      stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/Jan/Sun[last]"));
+
+  TEST_EQUAL(stream_c_locale<CharT>(std::chrono::year_month_weekday_last{
+                 std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("1970/Jan/Sun[last]"));
 
 #if defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32768 is not a valid year/jan/Dim[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/0 is not a valid month/Dim[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("-32767/jan/8 is not a valid weekday[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/jan/Dim[last]"));
-
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("1970/jan/Dim[last]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32768 is not a valid year/jan/Dim[last]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/0 is not a valid month/Dim[last]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+      SV("-32767/jan/8 is not a valid weekday[last]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/jan/Dim[last]"));
+
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+                 std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("1970/jan/Dim[last]"));
 #else  //  defined(__APPLE__)
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32768 is not a valid year/janv./dim.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/0 is not a valid month/dim.[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("-32767/janv./8 is not a valid weekday[last]"));
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/janv./dim.[last]"));
-
-  assert(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("1970/janv./dim.[last]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32768 is not a valid year/janv./dim.[last]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/0 is not a valid month/dim.[last]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+      SV("-32767/janv./8 is not a valid weekday[last]"));
+  TEST_EQUAL(
+      stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/janv./dim.[last]"));
+
+  TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::year_month_weekday_last{
+                 std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("1970/janv./dim.[last]"));
 #endif //  defined(__APPLE__)
 
 #if defined(__APPLE__)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32768 is not a valid year/ 1/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/0 is not a valid month/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("-32767/ 1/8 is not a valid weekday[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/ 1/日[last]"));
-
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("1970/ 1/日[last]"));
-#else    // defined(__APPLE__)
-#  if defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32768 is not a valid year/1月/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/0 is not a valid month/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("-32767/1月/8 is not a valid weekday[last]"));
-
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/1月/日[last]"));
-
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("1970/1月/日[last]"));
-#  else  // defined(_WIN32) || defined(_AIX)
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32768 is not a valid year/ 1月/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/0 is not a valid month/日[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}) ==
-         SV("-32767/ 1月/8 is not a valid weekday[last]"));
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("-32767/ 1月/日[last]"));
-
-  assert(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
-             std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}) ==
-         SV("1970/ 1月/日[last]"));
-#  endif // defined(_WIN32) || defined(_AIX)
-#endif   // defined(__APPLE__)
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32768 is not a valid year/ 1/日[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/0 is not a valid month/日[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+      SV("-32767/ 1/8 is not a valid weekday[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/ 1/日[last]"));
+
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+                 std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("1970/ 1/日[last]"));
+#elif defined(_WIN32) // defined(__APPLE__)
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32768 is not a valid year/1/日[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/0 is not a valid month/日[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+      SV("-32767/1/8 is not a valid weekday[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/1/日[last]"));
+
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+                 std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("1970/1/日[last]"));
+#elif defined(_AIX)   // defined(__APPLE__)
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32768 is not a valid year/1月/日[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/0 is not a valid month/日[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+      SV("-32767/1月/8 is not a valid weekday[last]"));
+
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/1月/日[last]"));
+
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+                 std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("1970/1月/日[last]"));
+#else                 // defined(__APPLE__)
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'768}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32768 is not a valid year/ 1月/日[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{0}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/0 is not a valid month/日[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{8}}}),
+      SV("-32767/ 1月/8 is not a valid weekday[last]"));
+  TEST_EQUAL(
+      stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+          std::chrono::year{-32'767}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+      SV("-32767/ 1月/日[last]"));
+
+  TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::year_month_weekday_last{
+                 std::chrono::year{1970}, std::chrono::month{1}, std::chrono::weekday_last{std::chrono::weekday{0}}}),
+             SV("1970/ 1月/日[last]"));
+#endif                // defined(__APPLE__)
 }
 
 int main(int, char**) {


        


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