Converting From unittest to pytest#

Conversion Checklist#

Note

Please bear in mind the following checklist is for general use; there may be some cases which require extra context or thought before implementing these changes.

  1. Before making any manual changes, run dannysepler/pytestify on the file. This does a lot of the brunt work for you!

  2. Check for references to iris.tests.IrisTest. If a class inherits from this, remove the inheritance. Inheritance is unnecessary for pytest tests, so iris.tests.IrisTest has been deprecated and its convenience methods have been moved to the iris.tests._shared_utils module.

  3. Check for references to unittest. Many of the functions within unittest are also in pytest, so often you can just change where the function is imported from.

  4. Check for references to self.assert. Pytest has a lighter-weight syntax for assertions, e.g. assert x == 2 instead of assertEqual(x, 2). In the case of custom IrisTest assertions, the majority of these have been replicated in iris.tests._shared_utils, but with snake_case instead of camelCase. Some iris.tests.IrisTest assertions have not been converted into iris.tests._shared_utils, as these were deemed easy to achieve via simple assert ... statements.

  5. Check for references to setUp(). Replace this with _setup() instead. Ensure that this is decorated with @pytest.fixture(autouse=True).

    @pytest.fixture(autouse=True)
def _setup(self):
   ...

  6. Check for references to @tests. These should be changed to @_shared_utils.

  7. Check for references to with mock.patch("..."). These should be replaced with mocker.patch("..."). mocker is a fixture, and can be passed into functions.

  8. Check for np.testing.assert.... This can usually be swapped for _shared_utils.assert....

  9. Check for references to super(). Most test classes used to inherit from iris.tests.IrisTest, so references to this should be removed.

  10. Check for references to self.tmp_dir. In pytest, tmp_path is used instead, and can be passed into functions as a fixture.

  11. Check for if __name__ == 'main'. This is no longer needed with pytest.

  12. Check for mock.patch("warnings.warn"). This can be replaced with pytest.warns(match=message).

  13. Check the file against astral-sh/ruff , using pip install ruff -> ruff check --select PT <file>.

Common Translations#

unittest method

pytest equivalent

assertTrue(x)

assert x

assertFalse(x)

assert not x

assertRegex(x, y)

assert re.match(y, x)

assertRaisesRegex(cls, msg_re)

with pytest.raises(cls, match=msg_re):

mock.patch(...)

mocker.patch(...)