fast-check

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About

fast-check is ranked #1 of 27 in property-based testing tools on Inferse. It runs on API, Linux, Web. There is a free plan.

Compared on property-based testing tools

Free plan: Yesfast-check.dev
Supported languages: JavaScript, TypeScriptfast-check.dev
Test runner support: Jest, Mocha, Vitest, Ava, Bun, Deno, Node.js test runnerfast-check.dev
Failing-case shrinking: Yesfast-check.dev
Stateful testing: Yesfast-check.dev
Reproducible failures: Yesfast-check.dev

Facts

Purpose: fast-check is a property-based testing library for JavaScript and TypeScript that generates inputs, runs assertions over many cases, and shrinks failures to smaller counterexamples.fast-check.dev · 30 Sept 2026
Testing workflow: The library is test-runner agnostic and works with Jest, Mocha, Vitest, and other test runners.fast-check.dev · 30 Sept 2026
Test building blocks: Tests use arbitraries to generate values, properties to specify expected behavior, runners to execute properties, and plugins to extend runners.fast-check.dev · 30 Sept 2026
Configuration: Users can configure runs, seeds, generated value sizes, time limits, and result reporting globally or per assertion.fast-check.dev · 30 Sept 2026
Failure diagnosis: When a property fails, fast-check shrinks the input to a smaller counterexample and reports information that helps diagnose the failure.github.com · 30 Sept 2026
Additional testing: The project describes fuzzing and generative testing for finding issues including race conditions and prototype poisoning.fast-check.dev · 30 Sept 2026
Integrations: The ecosystem lists official integrations for AVA, Jest, and Vitest, along with connectors for libraries such as Zod and io-ts.fast-check.dev · 30 Sept 2026
Security testing: The ecosystem documents an official @fast-check/poisoning package for checking whether specially crafted inputs cause global prototype modifications.fast-check.dev · 30 Sept 2026
Runtime requirements: The repository lists fast-check 5.x as requiring Node.js 22.12.0 or later, ECMAScript 2025, and optionally TypeScript 5.8 or later.github.com · 30 Sept 2026
Open source: The GitHub repository identifies fast-check as a public project released under the MIT license.github.com · 30 Sept 2026
Support: The project invites code and non-code contributions, community help, and financial support through GitHub Sponsors or OpenCollective.fast-check.dev · 30 Sept 2026
Ecosystem limitations: The ecosystem page says it can provide stability and maintenance details for official packages, but no specific guarantees for non-official packages.fast-check.dev · 30 Sept 2026