Repository: psf/black
File: fuzz.py (Python)

Code before:
"""Property-based tests for Black.

By Zac Hatfield-Dodds, based on my Hypothesmith tool for source code
generation.  You can run this file with `python`, `pytest`, or (soon)
a coverage-guided fuzzer I'm working on.
"""

import re

import hypothesmith
from hypothesis import HealthCheck, given, settings, strategies as st

import black
from blib2to3.pgen2.tokenize import (  # NB: This intends to (and currently does) import the black-vendored blib2to3
    TokenError,
)


# This test uses the Hypothesis and Hypothesmith libraries to generate random
# syntatically-valid Python source code and run Black in odd modes.
@settings(
    max_examples=1000,  # roughly 1k tests/minute, or half that under coverage
    derandomize=True,  # deterministic mode to avoid CI flakiness
    deadline=None,  # ignore Hypothesis' health checks; we already know that
    suppress_health_check=HealthCheck.all(),  # this is slow and filter-heavy.
)
@given(
    # Note that while Hypothesmith might generate code unlike that written by
    # humans, it's a general test that should pass for any *valid* source code.
    # (so e.g. running it against code scraped of the internet might also help)
    src_contents=hypothesmith.from_grammar() | hypothesmith.from_node(),
    # Using randomly-varied modes helps us to exercise less common code paths.
    mode=st.builds(
        black.FileMode,
        line_length=st.just(88) | st.integers(0, 200),
        string_normalization=st.booleans(),
        is_pyi=st.booleans(),
    ),
)

Review comment (suggestion):
I added this comment based on a memory of reading some code that variously imported either the `blib2to3` code or Python's built-in `lib2to3` code.  But after checking it again, I realize they use different module names, so I think this comment is redundant and can be removed.

Code after:
"""Property-based tests for Black.

By Zac Hatfield-Dodds, based on my Hypothesmith tool for source code
generation.  You can run this file with `python`, `pytest`, or (soon)
a coverage-guided fuzzer I'm working on.
"""

import re

import hypothesmith
from hypothesis import HealthCheck, given, settings, strategies as st

import black
from blib2to3.pgen2.tokenize import TokenError


# This test uses the Hypothesis and Hypothesmith libraries to generate random
# syntatically-valid Python source code and run Black in odd modes.
@settings(
    max_examples=1000,  # roughly 1k tests/minute, or half that under coverage
    derandomize=True,  # deterministic mode to avoid CI flakiness
    deadline=None,  # ignore Hypothesis' health checks; we already know that
    suppress_health_check=HealthCheck.all(),  # this is slow and filter-heavy.
)
@given(
    # Note that while Hypothesmith might generate code unlike that written by
    # humans, it's a general test that should pass for any *valid* source code.
    # (so e.g. running it against code scraped of the internet might also help)
    src_contents=hypothesmith.from_grammar() | hypothesmith.from_node(),
    # Using randomly-varied modes helps us to exercise less common code paths.
    mode=st.builds(
        black.FileMode,
        line_length=st.just(88) | st.integers(0, 200),
        string_normalization=st.booleans(),
        is_pyi=st.booleans(),
    ),
)
def test_idempotent_any_syntatically_valid_python(
    src_contents: str, mode: black.FileMode