[LLVMdev] [Patch] Adding unit tests to LLVM

[Talin]

Mark Kromis wrote:
> On Dec 27, 2008, at 7:41 PM, Misha Brukman wrote:
>> 2008/12/27 Mark Kromis <greybird at mac.com>
>> Just a curiosity question, why push for gtest vs Boost Test or a 
>> different test suite?
>> I normally use Boost, and their test suite, so I'm more familiar with 
>> that. So I was wondering is one better then the other, or is it just 
>> that someone makes a patch for it?
I did a very minimal amount of research into unit testing frameworks 
before I started using gtest for my own work. Since then I've become 
quite familiar with gtest's features, which made it a natural choice for 
me. I presume that other testing frameworks will have their own 
defenders on this list, and I am certainly willing to listen to what 
they have to say.

The unit test comparison article mentioned earlier 
(http://gamesfromwithin.com/?p=29) is a good starting point for 
evaluating different unit test frameworks. Although gtest is too new to 
have been mentioned in the article directly, if you actually compare 
gtest's features against the various criteria used by the author of the 
article, it comes off quite well.

Note that the author of the article later went and created his own unit 
test framework (UnitTest++), based on his experience with all of the 
other frameworks he tested. This was the only framework that I seriously 
looked at other than gtest, and I found it to be a bit too minimal for 
what I needed.
>> I looked more into Boost.Test to see what's in it.  Boost.Test 
>> doesn't seem to be stand-alone -- I don't see a way to use Boost.Test 
>> without importing some other chunks of Boost that the testing library 
>> depends on.  While Boost is a fine set of libraries, I don't think we 
>> want to increase the LLVM distribution by sizeof(Boost) just to 
>> enable unittesting, nor do we want to spend the time on maintaining a 
>> subset of Boost that's "just enough" to build and use the unittest 
>> library, along a modified configure/build process that Boost wants to 
>> use (Boost.Build? Boost.Jam?).
Although I haven't actually tried Boost.Test, I kind of figured that 
this would be the case - that you pretty much have to drink the "Boost 
Kool-Aid" in order to use it.
> So are you planning on maintaining whatever test system, or just have 
> them as a pre-requisite. For example are you going to have the gtest 
> incorporated, or have them install it separately first? I was under 
> the impression that the user would have to install gtest first.
So the plan is to take a snapshot of gtest and check it in to the LLVM 
tree, rather than have it installed separately. I was able to integrate 
gtest into LLVM's build system fairly easily, as gtest is designed to be 
integrated into a foreign build system - basically I just ignored the 
makefile that comes with gtest, and wrote an LLVM-style makefile rule 
for it. There's a special source file in gtest which includes all other 
sources that is intended for just such a purpose. I did not need to 
modify the gtest sources in any way.

This means that keeping the gtest snapshot up to date will be trivial, 
since it will only require copying in the latest gtest snapshot and 
checking it in to LLVM - presuming that gtest remains backwards 
compatible, which I assume it will.

Licensing-wise, both LLVM and gtest are distributed under a fairly 
permissive BSD-style license. I don't know who would make the judgement 
call as to whether or not the licenses can co-exist. However, since 
neither license is "viral" in the sense of wanting to apply any sort of 
restriction on derived works or the "work as a whole", I see no barrier 
to shipping a combined product with different portions falling under 
different licenses. Thus, the unit tests themselves would still fall 
under the LLVM license, and linking the unit tests with gtest would not 
violate either license. Of course, IANAL.

 From a maintenance standpoint, we have already heard from several 
enthusiastic volunteers who are involved in both the development of LLVM 
and gtest. So I doubt there will be much problems on that score.

My personal goal is that one should be able to check out the head of 
LLVM on a generic Linux/OS-X system, with only the standard development 
environment (i.e. make/gcc/etc) and type "make unittest" and have the 
tests run.

In the longer term, I'd like to see LLVM have an automated build that 
runs the unit tests as part of the build. I noticed that gtest has an 
option to output test results in XML form, although I have not played 
with this personally, it might be useful in this regard.
>>
>> Boost also seems to want to use exceptions, and LLVM does not want 
>> to.  I'm not sure if there would be some difficulties in running a 
>> build where some libraries are compiled with no exceptions, some 
>> with, and the results are linked together.  At the best case, it 
>> would complicate our build system to be able to support different set 
>> of flags for building LLVM libraries vs. Boost.Test (and the rest of 
>> Boost that we import).
>
> http://www.boost.org/doc/libs/1_37_0/libs/utility/throw_exception.html
> #define BOOST_NO_EXCEPTIONS
>
>>
>> Sample usage of Boost.Test: 
>> http://svn.boost.org/svn/boost/trunk/libs/test/example/unit_test_example_12.cpp 
>>
>> Note the code at the end setting up the test suite -- this is 
>> boilerplate code that I think shouldn't be necessary to setup and run 
>> tests.
>>
>
>
> http://svn.boost.org/svn/boost/trunk/libs/test/example/unit_test_example_01.cpp 
>
> My test cases are not that in-depth, I'm much closer to sample 1. I 
> haven't found a reason to go that crazy yet.
>
>
>> Google Test, on the other hand, has no external dependencies, and is 
>> distributed as a dozen of .h/.cc files; supports Makefile, SCons, and 
>> Xcode; and doesn't use exceptions or RTTI.
>>
>
> Gtest is much more lightweight, no comparison there. I know that llvm 
> is not very good with exceptions, but should a test case system 
> support that?
>
>
>> Sample usage of GTest: 
>> http://code.google.com/p/googletest/source/browse/trunk/samples/sample5_unittest.cc 
>>
>> GTest-specific LOC besides the #include statement: 0.
>
> I think it links to a library as well.
>
>> Note that I'm not counting main() for either Boost or GTest, because 
>> both provide a standard main() for use with almost all test files.
>>
>> Misha
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>
> Also for a note of reference, your links to the examples are the most 
> advanced samples. So boost can do more, thus has more weight/bloat 
> behind it.
>
> Were the other test kits looked at? Is gtest the best solution for the 
> project.
>
> Is this something your planning as putting in the tree, thus require 
> pulling in changes from google (license allowing), or does user need 
> to have the libraries/headers pre-installed?
>
> My question was not to cause a battle, but I wanted to be sure we were 
> using the right test kit, and not just picking one just because.  For 
> example gtest is very light weight test kit, that can do the job, but 
> will the tests outgrow what the test kit can do, and cause a 
> conversion to a more advanced one later?
>
> Regards,
> Mark Kromis
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