Unmaintained: Following temporary directory fixture changes in pytest, I made a successor library, pytest-flake8-path. I recommend you use that instead.

A pytest fixture for testing flake8 plugins.

A quick example:

def test_simple_run(flake8dir):
    flake8dir.make_example_py(
        """
        x  = 1
    """
    )
    result = flake8dir.run_flake8()
    assert result.out_lines == [
        "./example.py:1:2: E221 multiple spaces before operator"
    ]

Use pip:

python -m pip install pytest-flake8dir

Python 3.6 to 3.10 supported.

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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 setup.py entrypoint, which makes tox the easiest way to guarantee this is ready as it will run setup.py install on your project before running tests.

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 example1.py and example2.py, each containing one line with an assignment:

def test_sample(flake8dir):
    flake8dir.make_py_files(
        example1="""
            x = 1
        """,
        example2="""
            y = 1
        """,
    )

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

For example:

def test_sample(flake8dir):
    flake8dir.make_example_py(
        """
        x = 1
    """
    )

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):
    flake8dir.make_setup_cfg(
        """
        [flake8]
        ignore = E101
    """
    )

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/foo.py, 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/foo.py",
        """
        x = 1
    """,
    )

Runs flake8 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 flake8 runs in an isolated manner - see source.

Represents the parsed output of a flake8 run.

The full string of output (stdout) generated by flake8.

The full string of error output (stderr) generated by flake8.

The exit code that the flake8 run exited with.

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 = "./example.py:1:2: E221 multiple spaces before operator"
assert expected in result.out_lines

Like out_lines, but for error output.