About fast-check
fast-check is a property based testing library for JavaScript and TypeScript. It generates many inputs to find edge cases that hand written tests often miss.
What it does
You describe a property that should hold for any valid input, and fast-check generates random values to try to break it. When it finds a failing case, it shrinks the input to a smaller example that is easier to read and debug. It works inside any test runner, so you do not need a special integration.
Key features
- Random input generation for properties
- Shrinking of failing inputs to small examples
- Works with Jest, Mocha, Vitest and others
- A quick start guide that takes about five minutes
Who it's for
JavaScript and TypeScript developers who want stronger tests for parsers, data code and other logic that has many possible inputs.
Pricing and good to know
fast-check is MIT licensed and free to use. The GitHub repository has about 5.2k stars. The project publishes tutorials and a blog, and it lists several open source projects that have used it to find bugs.
Highlights
- Generate random inputs for a property
- Shrink failing inputs to small examples
- Plug into Jest, Mocha, Vitest and others
- Quick start guide for new users
