[lldb-dev] [Openmp-dev] [cfe-dev] RFC: End-to-end testing

[David Greene via lldb-dev]

David Blaikie via Openmp-dev <openmp-dev at lists.llvm.org> writes:

> I have a bit of concern about this sort of thing - worrying it'll lead to
> people being less cautious about writing the more isolated tests.

That's a fair concern.  Reviewers will still need to insist on small
component-level tests to go along with patches.  We don't have to
sacrifice one to get the other.

> Dunno if they need a new place or should just be more stuff in test-suite,
> though.

There are at least two problems I see with using test-suite for this:

- It is a separate repository and thus is not as convenient as tests
  that live with the code.  One cannot commit an end-to-end test
  atomically with the change meant to be tested.

- It is full of large codes which is not the kind of testing I'm talking
  about.

Let me describe how I recently added some testing in our downstream
fork.

- I implemented a new feature along with a C source test.

- I used clang to generate asm from that test and captured the small
  piece of it I wanted to check in an end-to-end test.

- I used clang to generate IR just before the feature kicked in and
  created an opt-style test for it.  Generating this IR is not always
  straightfoward and it would be great to have better tools to do this,
  but that's another discussion.

- I took the IR out of opt (after running my feature) and created an
  llc-style test out of it to check the generated asm.  The checks are
  the same as in the original C end-to-end test.

So the tests are checking at each stage that the expected input is
generating the expected output and the end-to-end test checks that we go
from source to asm correctly.

These are all really small tests, easily runnable as part of the normal
"make check" process.

                     -David