tests: fix assertion rewriting when pytest is used

[benoit-pierre]

Change this into this.

[eli-schwartz]

• Isn't this generally supposed to be better handled with self.assert*() methods?

• I'm not enthusiastic about adding a new file to the root of the repository. Is it possible to inject this for example by doing it in an if block inside unittests/__init__.py and still trigger the rewriting before pytest actually imports the files with the asserts that you want to rewrite? I haven't tested it but it seems plausible.

[benoit-pierre]

It's normally done automatically, but because of the way the testsuite is run and/or the way tests are named, it does not work.

• Isn't this generally supposed to be better handled with self.assert*() methods?

Being able to just use assert is kind of one of the points in using pytest (why even bother with unittest?).

• I'm not enthusiastic about adding a new file to the root of the repository. Is it possible to inject this for example by doing it in an if block inside unittests/__init__.py and still trigger the rewriting before pytest actually imports the files with the asserts that you want to rewrite? I haven't tested it but it seems plausible.

There's no corresponding config option, or command line argument. Doing it in conftest.py means it's automatically only done when running with pytest (if you want to keep compatibility with using unittest).

[eli-schwartz]

Sorry, by if block I meant more a try block (conditional but a very different form of it).

try:
    import pytest
except ModuleNotFoundError:
    pass
else:
    pytest.register_assert_rewrite('unittests')

This should be harmless when running with unittest but still register the hook under pytest (while simultaneously avoiding the addition of "yet another repository root file").

[benoit-pierre]

OK, I found a simpler alternative way.