fast-check

fast-check is ranked #3 of 27 in property-based testing tools on The Geeks Club. It runs on API, Linux, Web. There is a free plan.

fast-check plans and pricing

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fast-check Free MIT-licensed JavaScript/TypeScript testing library github.com · 30 Sept 2026

Compared on property-based testing tools

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

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fast-check

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

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Where it ranks on The Geeks Club

Best Property-Based Testing Tools in 2026#3 of 27

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Sources

fast-check.dev/docs/introduction/· checked 30 Sept 2026
fast-check.dev· checked 30 Sept 2026
fast-check.dev/docs/core-blocks/· checked 30 Sept 2026
fast-check.dev/docs/configuration/· checked 30 Sept 2026
github.com/dubzzz/fast-check· checked 30 Sept 2026
fast-check.dev/docs/ecosystem/· checked 30 Sept 2026
fast-check.dev/docs/support-us/· checked 30 Sept 2026