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Head-to-head · Property-Based Testing Tools

fast-check vs Hypothesis

  • Updated Nov 2026
  • Both researched from official sources
  • 4 checks side by side
Higher score fast-check #1 in Property-Based Testing Tools 9.4/10 Open source Free plan✓ 3 of 3 features Visit fast-check
Hypothesis #2 in Property-Based Testing Tools 9.3/10 Free plan Free plan✓ 3 of 3 features Visit Hypothesis

fast-check leads on 0 checks, Hypothesis on 0, and 4 are even. Who comes out ahead on the 4 yes/no, price and count checks where we have data for both products. The editor score weighs everything else too.

Our verdict

  • Highest scorefast-check · 9.4/10
  • Free planboth

fast-check scores higher on our rubric for property-based testing tools: 9.4 against 9.3 out of 10; our editors rank them #1 and #2.

fast-check is the better fit for javaScript and TypeScript teams. Hypothesis is the better fit for python teams using pytest.

  • fast-check fits best

    JavaScript and TypeScript teams

  • Hypothesis fits best

    Python teams using pytest

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Side by side

Feature fast-check 9.4/10 Visit ↗ Hypothesis 9.3/10 Visit ↗
At a glance
Editor score 9.4 9.3
Ranking #1 in Property-Based Testing Tools #2 in Property-Based Testing Tools
Best for JavaScript and TypeScript teams Python teams using pytest
Pricing model Free Free
Starting price Open source Free plan
Free plan ✓ ✓
Free trial — —
Deployment Self-hosted Desktop
Platforms Web Windows, macOS, Linux
Support Docs, Community Docs, Community
Integrations 7 integrations 2 integrations
Built for Solo, Small business, Mid-market, Enterprise Solo, Small business, Mid-market, Enterprise
Features fast-check 3/3 · Hypothesis 3/3
Failing-case shrinking ✓ ✓
Stateful testing ✓ ✓
Reproducible failures ✓ ✓
Specs
Supported languages JavaScript, TypeScript Python
Test runner support Jest, Mocha, Vitest, Ava, Bun, Deno, Node.js test runner pytest, unittest
Cases per run Not checked yet Not checked yet
Our review
Pros
  • Shrinks failures and supports deterministic replay with seeds and paths
  • Supports stateful, asynchronous, fuzzing, and scheduler-based testing
  • Integrates with Jest, Mocha, Vitest, Ava, Bun, Deno, and Node.js
  • Generates edge cases and automatically shrinks failing inputs
  • Supports rule-based stateful testing and failure replay
  • Works with both pytest and unittest across Windows, macOS, and Linux
Cons
  • Its scope is limited to JavaScript and TypeScript
  • Advanced stateful and scheduler workflows require thoughtful test design
  • It does not provide AI-assisted testing features
  • Supports Python rather than multiple programming languages
  • Requires pytest or unittest instead of providing a standalone test runner
  • Property-based tests require teams to define strategies and properties
Our verdict

fast-check is an open-source property-based testing library for JavaScript and TypeScript. It generates inputs, runs properties repeatedly, and reduces failing inputs to smaller cases that are easier to investigate. The library suits teams…

Read the review →

Hypothesis is an open-source Python library for property-based testing. Developers define input strategies and properties, then it generates test cases to explore how code behaves, including unusual edge cases. It is aimed at Python teams…

Read the review →
  1. fast-checkProperty-Based Testing Tools 9.4Open source
  2. HypothesisProperty-Based Testing Tools 9.3Free plan

Strengths and trade-offs

  • fast-check — where it wins

    • Shrinks failures and supports deterministic replay with seeds and paths
    • Supports stateful, asynchronous, fuzzing, and scheduler-based testing
    • Integrates with Jest, Mocha, Vitest, Ava, Bun, Deno, and Node.js

    Where it doesn't

    • Its scope is limited to JavaScript and TypeScript
    • Advanced stateful and scheduler workflows require thoughtful test design
    • It does not provide AI-assisted testing features

  • Hypothesis — where it wins

    • Generates edge cases and automatically shrinks failing inputs
    • Supports rule-based stateful testing and failure replay
    • Works with both pytest and unittest across Windows, macOS, and Linux

    Where it doesn't

    • Supports Python rather than multiple programming languages
    • Requires pytest or unittest instead of providing a standalone test runner
    • Property-based tests require teams to define strategies and properties

fast-check vs Hypothesis: questions

Which is better for Property-Based testing tools, fast-check or Hypothesis?

fast-check scores higher on our rubric for property-based testing tools: 9.4 against 9.3 out of 10; our editors rank them #1 and #2.

How do fast-check and Hypothesis compare?

All 4 checks we put side by side come out level: neither leads on any.

Do fast-check and Hypothesis have a free plan?

fast-check: Yes. Hypothesis: Yes.

More comparisons

All Property-Based testing tools comparisons → · Full ranking →

Reviewed by iTechGuides Editors · Editorial team · Updated Nov 2026

Last updated · How we research and update