Hypothesis

Hypothesis is the property-based testing library for Python. Instead of writing individual examples, tests describe properties that should hold for all inputs in a given range.

Hypothesis then randomly chooses which inputs to check, including edge cases the developer might not have thought about, using strategies that describe the data to generate, for example lists of integers or floats.

Hypothesis is open source and actively developed on GitHub; version 6.170.2 was released in October 2026.