The tests and the unittests both unconditionally call setup_vsenv()
because all tests are run using the backend commands directly: ninja,
msbuild, etc.
There's no way to undo this vs env setup, so the only way to test that
--vsenv works is by:
1. Removing all paths in PATH that provide ninja
2. Changing setup_vsenv(force=True) to forcibly set-up a new vsenv
when MESON_FORCE_VSENV_FOR_UNITTEST is set
3. Mock-patching build_command, test_command, install_command to use
`meson` instead of `ninja`
4. Asserting that 'Activating VS' is in the output for all commands
5. Ensure that compilation works because ninja is picked up from the
vs env.
I manually checked that this test actually does fail when the previous
commit is reverted.
assertTrue and assertFalse are recommended against, if you can get a
more specific assertion. And sometimes it is considerably shorter, for
example we have a custom assertPathExists which we can take advantage
of.
Jussi Pakkanen
Nirbheek Chauhan
Eli Schwartz
Xavier Claessens
Dylan Baker