Flake8-AAA¶
A linter for Python tests.
Flake8-AAA enforces simple formatting of your test suite making it more consistent and easier to grok, especially across teams.
Installation and usage¶
Flake8-AAA is a Flake8 plugin.
Install flake8-aaa
with pip
, which will also install flake8
:
$ pip install flake8-aaa
Invoke Flake8 on your test suite, in this case in the tests
directory:
$ flake8 tests
Errors returned by Flake8-AAA have the AAA code, for example:
tests/block/test_init.py:14:1: AAA02 multiple Act blocks found in test
Arrange Act Assert¶
Tests are linted against the Arrange Act Assert pattern.
TL;DR following the AAA pattern means tests are laid out like this:
def test():
"""
__docstring__
"""
<ARRANGE block> # set up of the system under test (SUT)
<ACT block> # perform a single action on the SUT
<ASSERT block> # check that the SUT changed as expected
For example:
def test(tmpdir):
"""
Checker is able to parse provided file at load time
"""
target_file = tmpdir.join('test.py')
target_file.write('assert 1 + 2 == 3\n')
tree = ast.parse(target_file.read())
checker = Checker(tree, ['assert 1 + 2 == 3\n'], target_file.strpath)
result = checker.load()
assert result is None
assert len(checker.tree.body) == 1
assert type(checker.tree.body[0]) == ast.Assert
assert len(checker.ast_tokens.tokens) == 8
More examples are in our test suite’s “good” files.
Compatibility¶
- Pytest and unittest supported.
- Compatible with Black and yapf formatted code.
- Compatible with type-annotated code, checked with mypy.
- Current release works with the latest versions of Python 3 (3.6, 3.7 and 3.8). Older releases have support for older Pythons.
See the Compatibility list for more info.