hypothesis

The property-based testing library for Python

hypothesis Copyleft license MPL-2.0 Active ★ 8,883 v6.165.5 released 2026-08-12

Install

hypothesis on PyPI

pip

pip install hypothesis

uv

uv add hypothesis

poetry

poetry add hypothesis

Package facts

License	MPL-2.0 (copyleft)
Python support	supports the current Python release (>=3.10)
Install friction	medium — platform-specific wheel
Runtime dependencies	2 — exceptiongroup, sortedcontainers
Maintenance	actively maintained — 1 days since the last release
Last repo commit	2026-08-12
First released	2013-03-10
Popularity	one of the top 1,000 most-downloaded packages on PyPI (30-day window, as of 2026-08-13)
Known vulnerabilities	none known (OSV.dev, checked 2026-08-13)

Evidence: hypothesis-6.165.5-cp310-abi3-macosx_10_12_x86_64.whl; hypothesis-6.165.5-cp310-abi3-macosx_11_0_arm64.whl; hypothesis-6.165.5-cp310-abi3-manylinux_2_17_aarch64.manylinux2014_aarch64.whl; hypothesis-6.165.5-cp310-abi3-manylinux_2_17_armv7l.manylinux2014_armv7l.whl; hypothesis-6.165.5-cp310-abi3-manylinux_2_17_x86_64.manylinux2014_x86_64.whl; hypothesis-6.165.5-cp310-abi3-manylinux_2_31_riscv64.whl; hypothesis-6.165.5-cp310-abi3-manylinux_2_5_i686.manylinux1_i686.whl; hypothesis-6.165.5-cp310-abi3-musllinux_1_2_aarch64.whl; hypothesis-6.165.5-cp310-abi3-musllinux_1_2_armv7l.whl; hypothesis-6.165.5-cp310-abi3-musllinux_1_2_riscv64.whl; hypothesis-6.165.5-cp310-abi3-musllinux_1_2_x86_64.whl; hypothesis-6.165.5-cp310-abi3-win32.whl; hypothesis-6.165.5-cp310-abi3-win_amd64.whl; hypothesis-6.165.5-cp310-cp310-macosx_10_12_x86_64.whl; hypothesis-6.165.5-cp310-cp310-macosx_11_0_arm64.whl; hypothesis-6.165.5-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl; hypothesis-6.165.5-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl; hypothesis-6.165.5-cp310-cp310-musllinux_1_2_aarch64.whl; hypothesis-6.165.5-cp310-cp310-musllinux_1_2_x86_64.whl; hypothesis-6.165.5-cp310-cp310-win_amd64.whl

Keywords: python, testing, fuzzing, property-based-testing

Development Status :: 5 - Production/StableFramework :: HypothesisFramework :: PytestIntended Audience :: DevelopersOperating System :: Microsoft :: WindowsOperating System :: POSIXOperating System :: UnixProgramming Language :: PythonProgramming Language :: Python :: 3Programming Language :: Python :: 3 :: OnlyProgramming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Programming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPyTopic :: Education :: TestingTopic :: Software Development :: TestingTyping :: Typed

About hypothesis

from the package's own PyPI description — quoted content, verbatim

Hypothesis

Hypothesis is the property-based testing library for Python. With Hypothesis, you write tests which should pass for all inputs in whatever range you describe, and let Hypothesis randomly choose which of those inputs to check - including edge cases you might not have thought about. For example:

from hypothesis import given, strategies as st


@given(st.lists(st.integers()))
def test_matches_builtin(ls):
    assert sorted(ls) == my_sort(ls)

This randomized testing can catch bugs and edge cases that you didn't think of and wouldn't have found. In addition, when Hypothesis does find a bug, it doesn't just report any failing test case — it reports the simplest possible one....

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AI interpretation — verify before relying

AI-generated interpretation of the package facts above; every digit, version, license, or vulnerability id it cites is grounded in the facts already shown on this page

Hypothesis is a property-based testing library that generates random test inputs across a specified range to find edge cases and bugs, then shrinks failing cases to their simplest form for easier debugging.

Medium install friction with two lightweight runtime dependencies (exceptiongroup, sortedcontainers). Active maintenance with release 1 day old and 8883 GitHub stars; supports Python 3.10–3.14 and PyPy with broad platform coverage via prebuilt wheels.

Licensed under MPL-2.0 (copyleft), requiring derivative works and modifications to be distributed under the same license; suitable for internal testing but review required before redistributing modified versions.

Usage

pip install hypothesis

from hypothesis import given, strategies as st

@given(st.lists(st.integers()))
def test_my_function(data):
    assert my_function(data) == expected_result(data)

Requires Python 3.10 or later; intended for use within test suites (pytest or unittest compatible).

Verdict: Hypothesis is a mature, actively maintained property-based testing tool with strong community adoption (top 1000 PyPI). MPL-2.0 copyleft licensing requires attention in proprietary contexts. Zero known vulnerabilities and straightforward installation make it a reliable choice for developers seeking to catch subtle bugs through randomized, shrinkable test cases.

Needs verification

Whether optional extras (mentioned in description) introduce additional dependencies or friction beyond the two runtime deps listed
Performance characteristics and memory overhead when testing large input spaces or complex data structures

property-based testing pythonrandom test case generationfuzzing library pythonhypothesis testing frameworkautomated edge case findertest input shrinkinggenerative testing python