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"""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 hypothesmith
from hypothesis import HealthCheck, given, settings
from hypothesis import strategies as st
import black
# This test uses the Hypothesis and Hypothesmith libraries to generate random
# syntatically-valid Python source code and run Black in odd modes.
    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=list(HealthCheck),  # this is slow and filter-heavy.
    # 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(),
        preview=st.booleans(),
        is_pyi=st.booleans(),
        magic_trailing_comma=st.booleans(),
def test_idempotent_any_syntatically_valid_python(
    src_contents: str, mode: black.FileMode
        "#\r" in src_contents or "\\\n" in src_contents
    ) and black.Preview.normalize_cr_newlines not in mode:
        return
    # Before starting, let's confirm that the input string is valid Python:
    compile(src_contents, "<string>", "exec")  # else the bug is in hypothesmith
    # Then format the code...
    dst_contents = black.format_str(src_contents, mode=mode)
    # And check that we got equivalent and stable output.
    black.assert_equivalent(src_contents, dst_contents)
    black.assert_stable(src_contents, dst_contents, mode=mode)
    # Future test: check that pure-python and mypyc versions of black
    # give identical output for identical input?
if __name__ == "__main__":
    # Run tests, including shrinking and reporting any known failures.
    test_idempotent_any_syntatically_valid_python()
    # If Atheris is available, run coverage-guided fuzzing.
    # (if you want only bounded fuzzing, just use `pytest fuzz.py`)
        import sys
        import atheris
    except ImportError:
        pass
        test = test_idempotent_any_syntatically_valid_python
        atheris.Setup(
            sys.argv,
            test.hypothesis.fuzz_one_input,  # type: ignore[attr-defined]
        atheris.Fuzz()

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