Putting smart fuzzing into the world's best testing workflow for Python.

Property-based tests using Hypothesis fit cleanly into any Python test suite - while being faster to write, better at finding bugs, and giving clearer design feedback than traditional example-based unit tests. That's why everyone serious about testing Python code uses it - from companies like Google and Amazon, to open source projects like Numpy or dateutil, to high-school students and professors of astrophysics.

HypoFuzz runs your property-based test suite, using cutting-edge fuzzing techniques and coverage instrumentation to find even the rarest inputs which trigger an error. Interleaving and prioritising your tests make it the most efficient way to spend compute instead of engineering time looking for bugs, and the Hypothesis database makes it easy to reproduce and diagnose errors when you're ready to deal with them.

the newsletter

HypoFuzz is still young, so we'll have plenty to share as we roll out new features - and the first place you'll hear about them is our low-volume newsletter.

Get started

Whether you're a corporate team or a community nonprofit, we've got a plan for you. And if you want an expert to help you get started - or unstuck - we also offer training, consulting, and more.

View pricing »


HypoFuzz fits seamlessly into your workflow, with a familiar CLI and a live dashboard to monitor progress. Any questions about how to get set up to find bugs, or reproduce bugs that you've found? Our docs have you covered.

Read the docs »


Hypothesis is world-leading library for property-based testing, and used by thousands of companies and Python projects who are serious about finding bugs.

Learn more »