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A pytest fixture for testing flake8 plugins.

Project description pre-commit

A pytest fixture for testing flake8 plugins.

A quick example:

def test_simple_run(flake8dir):
        x  = 1
    result = flake8dir.run_flake8()
    assert result.out_lines == [
        './ E221 multiple spaces before operator'


Use pip:

python -m pip install pytest-flake8dir

Python 3.6 to 3.9 supported.

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flake8dir fixture

A pytest fixture that wraps Pytest’s built-in tmpdir fixture (docs), to create a temporary directory, allow adding files, and running flake8.

If you’re using this to test a flake8 plugin, make sure flake8 is picking up your plugin during tests. Normally this is done with a entrypoint, which makes tox the easiest way to guarantee this is ready as it will run install on your project before running tests.

flake8dir.make_py_files(**kwargs: Mapping[str, str])

Creates one python file for each passed keyword argument, with name corresponding to the keyword argument + ‘.py’, and content according the string value of the argument. The value will be processed with textwrap.dedent() so mixed indentation is not a problem in your test files.

For example, this creates two python files in the temporary directory, called and, each containing one line with an assignment:

def test_sample(flake8dir):
            x = 1
            y = 1

flake8dir.make_example_py(content: str)

A shortcut for make_py_files(example=content), for when you are using a single file over and over. This creates just, which is often all you need for testing a rule.

For example:

def test_sample(flake8dir):
        x = 1

flake8dir.make_setup_cfg(contents: str)

Makes the file setup.cfg in the test directory with contents equal to the string passed in. This is again processed with textwrap.dedent() so indentation is not a worry. You’ll probably want to set the [flake8] section header to configure flake8.

For example, this makes flake8 ignore rule E101:

def test_sample(flake8dir):
        ignore = E101

flake8dir.make_file(filename: str, content: str)

Make an arbitrary file with the given filename - this function is the inner implementation for make_py_files and make_setup_cfg. filename may include directories, like mydir/, and they will be created. content is subject to the same textwrap.dedent() processing as mentioned above.

For example:

def test_sample(flake8dir):
    flake8dir.make_file('myfile/', '''
        x = 1

flake8dir.run_flake8(extra_args: List[str]=None) -> Flake8Result

Runs flake8 in the current process, and returns a Flake8Result representing the results.

extra_args may be a list of extra flags to pass to flake8, for example passing ['--ignore', 'E101'] would achieve the same thing as the above setup.cfg example. Note some arguments are already passed to ensure it runs in the same process without multiprocessing - see source.


Represents the parsed output of a flake8 run.

Flake8Result.out: str

The full string of output generated by flake8.

Flake8Result.exit_code: int

The exit code that the flake8 run exited with.

Flake8Result.out_lines: List[str]

A list of individual lines of output, without trailing newlines. This is the most useful tool for making assertions against.

For example, given a result you can check for a particular line being output:

result = flake8dir.run_flake8()
expected = './ E221 multiple spaces before operator'
assert expected in result.out_lines

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