8000 Add reproducibility test for `gzip.compress()` · Issue #131697 · python/cpython · GitHub
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za3k opened this issue Mar 24, 2025 · 0 comments
Open

Add reproducibility test for gzip.compress() #131697

za3k opened this issue Mar 24, 2025 · 0 comments
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tests Tests in the Lib/test dir type-feature A feature request or enhancement

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@za3k
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za3k commented Mar 24, 2025 •
edited by picnixz
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The issue #112346 was reported, which was a failure to keep reproducibility in gzip module output from Python 3.10 to 3.11.

There was a fix discussed and rejected in #112346

I think it makes sense not to actually change things back, but failing to merge the PR means we also failed to add unit tests.

Can we please add a general-purpose, fragile reproducibility test for the gzip module, so that this problem does not recur?

Ex. test that the output of gzip.compress("Hello world") remains stable

def test_gzip_reproducibility():
    """If this test fails, gzip.compress does not give reproducible output. Either fix that, or document the change in What's New and change the constant 'expected' below."""
    expected = b'\x1f\x8b\x08\x00\xa2\xd2\xe1g\x02\xff\xf3H\xcd\xc9\xc9W(\xcf/\xcaI\x01\x00R\x9e\xd6\x8b\x0b\x00\x00\x00'
    assert gzip.compress(b"Hello world") == expected

    expected = 
b'\x1f\x8b\x08\x00\x00\x00\x00\x00\x02\xff\xf3H\xcd\xc9\xc9W(\xcf/\xcaI\x01\x00R\x9e\xd6\x8b\x0b\x00\x00\x00'
    assert gzip.compress(b"Hello world", mtime=0) == expected
@za3k za3k added the type-bug An unexpected behavior, bug, or error label Mar 24, 2025
@picnixz picnixz changed the title Request for unit test Add reproducibility test for gzip.compress() Mar 24, 2025
@picnixz picnixz added type-feature A feature request or enhancement tests Tests in the Lib/test dir and removed type-bug An unexpected behavior, bug, or error labels Mar 24, 2025
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