As of bug 1339178 we are now running our python unittests with the 'pytest' framework. This was possible because pytest has the ability to run unittest-based tests out of the box, so most of the tests didn't need to be upgraded. But the pytest format is much simpler, cleaner and easier to read/write. Plus it has a ton of nifty features that are lacking from the unittest framework. To take full advantage of this, we should convert as many of our existing unittest-based tests to pytest as possible. In general, I think the migration would look something like this: 1) Convert all self.assertFoo functions to simple 'assert' statements. So: self.assertEquals(foo, 1) becomes: assert foo == 1 2) Move all test functions to top level module functions. So: class TestFoo(TestCase): def test_foo(self): ... becomes: def test_foo(): ... 3) Move all shared logic to pytest fixtures [1]. So: class TestFoo(TestCase): def helper(self): ... becomes: @pytest.fixture def helper(): ... def test_foo(helper): ... I think that should more or less cover most migrations. There will definitely be a few edge cases and some light refactoring required along the way, but it shouldn't be too bad. This is a tracking bug, so please file new bugs to convert specific test directories and make them block this bug. [1] https://docs.pytest.org/en/latest/fixture.html