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</h1>

<p align="center">
Property based testing framework for JavaScript/TypeScript
</p>

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## Getting started

Hands-on tutorial and definition of Property Based Testing: [🏁 see tutorial](https://fast-check.dev/docs/tutorials/quick-start/). Or directly try it online on our pre-configured [CodeSandbox](https://codesandbox.io/s/github/dubzzz/fast-check/tree/main/examples?previewwindow=tests).

Property based testing frameworks check the truthfulness of properties. A property is a statement like: _for all (x, y, ...) such that precondition(x, y, ...) holds predicate(x, y, ...) is true_.

Install the module with: `pnpm add -D fast-check` or `yarn add fast-check --dev` or `npm install fast-check --save-dev`

Example of integration in [mocha](http://mochajs.org/):

```js
import fc from 'fast-check';

// Code under test
const contains = (text, pattern) => text.indexOf(pattern) >= 0;

// Properties
describe('properties', () => {
  // string text always contains itself
  it('should always contain itself', () => {
    fc.assert(fc.property(fc.string(), (text) => contains(text, text)));
  });
  // string a + b + c always contains b, whatever the values of a, b and c
  it('should always contain its substrings', () => {
    fc.assert(
      fc.property(fc.string(), fc.string(), fc.string(), (a, b, c) => {
        // Alternatively: no return statement and direct usage of expect or assert
        return contains(a + b + c, b);
      }),
    );
  });
});
```

In case of failure, the test raises a red flag. Its output should help you to diagnose what went wrong in your implementation. Example with a failing implementation of contain:

```
1) should always contain its substrings
    Error: Property failed after 1 tests (seed: 1527422598337, path: 0:0): ["","",""]
    Shrunk 1 time(s)
    Got error: Property failed by returning false

    Hint: Enable verbose mode in order to have the list of all failing values encountered during the run
```

Integration with other test frameworks: [ava](https://github.com/dubzzz/fast-check-examples/blob/main/test-ava/example.spec.js), [jasmine](https://github.com/dubzzz/fast-check-examples/blob/main/test-jasmine/example.spec.js), [jest](https://github.com/dubzzz/fast-check-examples/blob/main/test-jest/example.spec.js), [mocha](https://github.com/dubzzz/fast-check-examples/blob/main/test/longest%20common%20substr/test.js) and [tape](https://github.com/dubzzz/fast-check-examples/blob/main/test-tape/example.spec.js).

More examples: [simple examples](https://github.com/dubzzz/fast-check/tree/main/examples), [fuzzing](https://github.com/dubzzz/fuzz-rest-api) and [against various algorithms](https://github.com/dubzzz/fast-check-examples).

Useful documentations:

- [🏁 Introduction to Property Based & Hands On](https://fast-check.dev/docs/tutorials/quick-start/)
- [🐣 Built-in arbitraries](https://fast-check.dev/docs/core-blocks/arbitraries/)
- [🔧 Custom arbitraries](https://fast-check.dev/docs/core-blocks/arbitraries/combiners/)
- [🏃‍♂️ Property based runners](https://fast-check.dev/docs/core-blocks/runners/)
- [💥 Tips](https://fast-check.dev/docs/configuration/)
- [🔌 API Reference](https://fast-check.dev/docs/api/)
- [⭐ Awesome fast-check](https://fast-check.dev/docs/ecosystem/)

## Why should I migrate to fast-check?

fast-check has initially been designed in an attempt to cope with limitations I encountered while using other property based testing frameworks designed for JavaScript:

- **Types:** strong and up-to-date types - _thanks to TypeScript_
- **Extendable:** easy `map` method to derive existing arbitraries while keeping shrink \[[more](https://fast-check.dev/docs/core-blocks/arbitraries/combiners/any/#map)\] - _some frameworks ask the user to provide both a->b and b->a mappings in order to keep a shrinker_
- **Extendable:** kind of flatMap-operation called `chain` \[[more](https://fast-check.dev/docs/core-blocks/arbitraries/combiners/any/#chain)\] - _able to bind the output of an arbitrary as input of another one while keeping the shrink working_
- **Extendable:** precondition checks with `fc.pre(...)` \[[more](https://fast-check.dev/docs/core-blocks/properties/#example)\] - _filtering invalid entries can be done directly inside the check function if needed_
- **Extendable:** easily switch from fake data in tests to property based with `fc.gen()` \[[more](https://fast-check.dev/docs/core-blocks/arbitraries/others/#gen)\] - _generate random values within your predicates_
- **Smart:** ability to shrink on `fc.oneof` \[[more](https://fast-check.dev/docs/core-blocks/arbitraries/combiners/any/#oneof)\] - _surprisingly some frameworks don't_
- **Smart:** biased by default - _by default it generates both small and large values, making it easier to dig into counterexamples without having to tweak a size parameter manually_
- **Debug:** verbose mode \[[more](https://fast-check.dev/docs/configuration/custom-reports/#verbosity)\]\[[tutorial](https://fast-check.dev/docs/tutorials/quick-start/read-test-reports/#how-to-increase-verbosity)\] - _easier troubleshooting with verbose mode enabled_
- **Debug:** replay directly on the minimal counterexample \[[tutorial](https://fast-check.dev/docs/tutorials/quick-start/read-test-reports/#how-to-re-run)\] - _no need to replay the whole sequence, you get directly the counterexample_
- **Debug:** custom examples in addition of generated ones \[[more](https://fast-check.dev/docs/configuration/user-definable-values/#run-against-custom-values)\] - _no need to duplicate the code to play the property on custom examples_
- **Debug:** logger per predicate run \[[more](https://fast-check.dev/docs/core-blocks/arbitraries/others/#context)\] - _simplify your troubleshoot with fc.context and its logging feature_
- **Unique:** model based approach \[[more](https://fast-check.dev/docs/advanced/model-based-testing/)\]\[[article](https://medium.com/criteo-labs/detecting-the-unexpected-in-web-ui-fuzzing-1f3822c8a3a5)\] - _use the power of property based testing to test UI, APIs or state machines_
- **Unique:** detect race conditions in your code \[[more](https://fast-check.dev/docs/advanced/race-conditions/)\]\[[tutorial](https://fast-check.dev/docs/tutorials/detect-race-conditions/)\] - _shuffle the way your promises and async calls resolve using the power of property based testing to detect races_
- **Unique:** simplify user definable corner cases \[[more](https://fast-check.dev/docs/configuration/user-definable-values/#shrink-custom-values)\] - _simplify bug resolution by asking fast-check if it can find an even simpler corner case_

For more details, refer to the documentation in the links above.

### Trusted

fast-check has been trusted for years by big projects like: [jest](https://github.com/jestjs/jest), [jasmine](https://github.com/jasmine/jasmine), [fp-ts](https://github.com/gcanti/fp-ts), [io-ts](https://github.com/gcanti/io-ts), [ramda](https://github.com/ramda/ramda), [js-yaml](https://github.com/nodeca/js-yaml), [query-string](https://github.com/sindresorhus/query-string)...

### Powerful

It also proved useful in finding bugs among major open source projects such as [jest](https://github.com/jestjs/jest), [query-string](https://github.com/sindresorhus/query-string)... and [many others](https://fast-check.dev/docs/introduction/track-record/).

## Compatibility

Here are the minimal requirements to use fast-check properly without any polyfills:

| fast-check | node                   | ECMAScript version | _TypeScript (optional)_ |
| ---------- | ---------------------- | ------------------ | ----------------------- |
| **4.x**    | ≥12.17.0<sup>(1)</sup> | ES2020             | ≥5.0                    |
| **3.x**    | ≥8<sup>(2)</sup>       | ES2017             | ≥4.1<sup>(3)</sup>      |
| **2.x**    | ≥8<sup>(2)</sup>       | ES2017             | ≥3.2<sup>(4)</sup>      |
| **1.x**    | ≥0.12<sup>(2)</sup>    | ES3                | ≥3.0<sup>(4)</sup>      |

<details>
<summary>More details...</summary>

1. Even if version 12.x should support most of the ES2020 features that will be leveraged by the version 4, we recommend relying at least on version 14.x of Node as it supports all the targeted specification. In addition, we highly encourage switching to still supported LTS versions of Node and not sticking to unsupported versions for too long.
2. Except for features that cannot be polyfilled - such as `bigint`-related ones - all the capabilities of fast-check should be usable given you use at least the minimal recommended version of node associated to your major of fast-check.
3. Require either lib or target ≥ ES2020 or `@types/node` to be installed.
4. Require either lib or target ≥ ES2015 or `@types/node` to be installed.

</details>

## Contributors ✨

Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/docs/en/emoji-key)):

<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
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<table>
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      <td align="center" valign="top" width="14.28%"><a href="https://github.com/dubzzz"><img src="https://avatars.githubusercontent.com/u/5300235?v=4?s=100" width="100px;" alt="Nicolas DUBIEN"/><br /><sub><b>Nicolas DUBIEN</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=dubzzz" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=dubzzz" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=dubzzz" title="Tests">⚠️</a> <a href="#infra-dubzzz" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a> <a href="#design-dubzzz" title="Design">🎨</a> <a href="#maintenance-dubzzz" title="Maintenance">🚧</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/hath995"><img src="https://avatars.githubusercontent.com/u/381037?v=4?s=100" width="100px;" alt="Aaron Elligsen"/><br /><sub><b>Aaron Elligsen</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=hath995" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=hath995" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=hath995" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/willheslam"><img src="https://avatars.githubusercontent.com/u/5377213?v=4?s=100" width="100px;" alt="Will Heslam"/><br /><sub><b>Will Heslam</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=willheslam" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/kazchimo"><img src="https://avatars.githubusercontent.com/u/31263328?v=4?s=100" width="100px;" alt="kazchimo"/><br /><sub><b>kazchimo</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=kazchimo" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=kazchimo" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/brandon-leapyear"><img src="https://avatars.githubusercontent.com/u/27799541?v=4?s=100" width="100px;" alt="Brandon Chinn"/><br /><sub><b>Brandon Chinn</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=brandon-leapyear" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=brandon-leapyear" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://safareli.github.io/resume/"><img src="https://avatars.githubusercontent.com/u/1932383?v=4?s=100" width="100px;" alt="Irakli Safareli"/><br /><sub><b>Irakli Safareli</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=safareli" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/TheSpyder"><img src="https://avatars.githubusercontent.com/u/298292?v=4?s=100" width="100px;" alt="Andrew Herron"/><br /><sub><b>Andrew Herron</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=TheSpyder" title="Documentation">📖</a> <a href="#plugin-TheSpyder" title="Plugin/utility libraries">🔌</a></td>
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      <td align="center" valign="top" width="14.28%"><a href="https://github.com/EricCrosson"><img src="https://avatars.githubusercontent.com/u/1596818?v=4?s=100" width="100px;" alt="Eric Crosson"/><br /><sub><b>Eric Crosson</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=EricCrosson" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=EricCrosson" title="Code">💻</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/burrscurr"><img src="https://avatars.githubusercontent.com/u/23213508?v=4?s=100" width="100px;" alt="burrscurr"/><br /><sub><b>burrscurr</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=burrscurr" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://www.dijonkitchen.org/"><img src="https://avatars.githubusercontent.com/u/11434205?v=4?s=100" width="100px;" alt="JC (Jonathan Chen)"/><br /><sub><b>JC (Jonathan Chen)</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=dijonkitchen" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://fixate.it/"><img src="https://avatars.githubusercontent.com/u/1510520?v=4?s=100" width="100px;" alt="Larry Botha"/><br /><sub><b>Larry Botha</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=larrybotha" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=larrybotha" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=larrybotha" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://epa.ms/RomanGusev"><img src="https://avatars.githubusercontent.com/u/5839225?v=4?s=100" width="100px;" alt="Roman Gusev"/><br /><sub><b>Roman Gusev</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=102" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://timwis.com/"><img src="https://avatars.githubusercontent.com/u/761444?v=4?s=100" width="100px;" alt="Tim Wisniewski"/><br /><sub><b>Tim Wisniewski</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=timwis" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://world.hey.com/brais"><img src="https://avatars.githubusercontent.com/u/17855450?v=4?s=100" width="100px;" alt="Brais Piñeiro"/><br /><sub><b>Brais Piñeiro</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=brapifra" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=brapifra" title="Tests">⚠️</a></td>
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      <td align="center" valign="top" width="14.28%"><a href="https://github.com/brds"><img src="https://avatars.githubusercontent.com/u/118620?v=4?s=100" width="100px;" alt="Renaud-Pierre Bordes"/><br /><sub><b>Renaud-Pierre Bordes</b></sub></a><br /><a href="#design-brds" title="Design">🎨</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/fwip"><img src="https://avatars.githubusercontent.com/u/190414?v=4?s=100" width="100px;" alt="Jemma Nelson"/><br /><sub><b>Jemma Nelson</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=fwip" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://fullof.bs/"><img src="https://avatars.githubusercontent.com/u/77482?v=4?s=100" width="100px;" alt="John Haugeland"/><br /><sub><b>John Haugeland</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=StoneCypher" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/treydavis"><img src="https://avatars.githubusercontent.com/u/1691239?v=4?s=100" width="100px;" alt="Trey Davis"/><br /><sub><b>Trey Davis</b></sub></a><br /><a href="#design-treydavis" title="Design">🎨</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://leonzalion.com/"><img src="https://avatars.githubusercontent.com/u/36966635?v=4?s=100" width="100px;" alt="Leon Si"/><br /><sub><b>Leon Si</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=leonzalion" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://spion.github.io/"><img src="https://avatars.githubusercontent.com/u/502412?v=4?s=100" width="100px;" alt="Gorgi Kosev"/><br /><sub><b>Gorgi Kosev</b></sub></a><br /><a href="#infra-spion" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/mayconsacht"><img src="https://avatars.githubusercontent.com/u/5214042?v=4?s=100" width="100px;" alt="mayconsacht"/><br /><sub><b>mayconsacht</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=mayconsacht" title="Code">💻</a></td>
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      <td align="center" valign="top" width="14.28%"><a href="https://github.com/paldepind"><img src="https://avatars.githubusercontent.com/u/521604?v=4?s=100" width="100px;" alt="Simon Friis Vindum"/><br /><sub><b>Simon Friis Vindum</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=paldepind" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=paldepind" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://twitter.com/gibson042"><img src="https://avatars.githubusercontent.com/u/1199584?v=4?s=100" width="100px;" alt="Richard Gibson"/><br /><sub><b>Richard Gibson</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=gibson042" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://alanharper.com.au/"><img src="https://avatars.githubusercontent.com/u/475?v=4?s=100" width="100px;" alt="Alan Harper"/><br /><sub><b>Alan Harper</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=aussiegeek" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/Osman-Sodefa"><img src="https://avatars.githubusercontent.com/u/90332566?v=4?s=100" width="100px;" alt="Makien Osman"/><br /><sub><b>Makien Osman</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=Osman-Sodefa" title="Code">💻</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/sommd"><img src="https://avatars.githubusercontent.com/u/7817485?v=4?s=100" width="100px;" alt="David Sommerich"/><br /><sub><b>David Sommerich</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=sommd" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=sommd" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/diegopedro94"><img src="https://avatars.githubusercontent.com/u/7157796?v=4?s=100" width="100px;" alt="Diego Pedro"/><br /><sub><b>Diego Pedro</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=diegopedro94" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=diegopedro94" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/BoruiGu"><img src="https://avatars.githubusercontent.com/u/8686167?v=4?s=100" width="100px;" alt="Borui Gu"/><br /><sub><b>Borui Gu</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=BoruiGu" title="Documentation">📖</a></td>
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      <td align="center" valign="top" width="14.28%"><a href="https://github.com/eventualbuddha"><img src="https://avatars.githubusercontent.com/u/1938?v=4?s=100" width="100px;" alt="Brian Donovan"/><br /><sub><b>Brian Donovan</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=eventualbuddha" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/volrk"><img src="https://avatars.githubusercontent.com/u/32265974?v=4?s=100" width="100px;" alt="volrk"/><br /><sub><b>volrk</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=volrk" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=volrk" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=volrk" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/tinydylan"><img src="https://avatars.githubusercontent.com/u/41112113?v=4?s=100" width="100px;" alt="tinydylan"/><br /><sub><b>tinydylan</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=tinydylan" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=tinydylan" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/jasikpark"><img src="https://avatars.githubusercontent.com/u/10626596?v=4?s=100" width="100px;" alt="Caleb Jasik"/><br /><sub><b>Caleb Jasik</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=jasikpark" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/rulai-hu"><img src="https://avatars.githubusercontent.com/u/2570932?v=4?s=100" width="100px;" alt="Rulai Hu"/><br /><sub><b>Rulai Hu</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=rulai-hu" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/afonsojramos"><img src="https://avatars.githubusercontent.com/u/19473034?v=4?s=100" width="100px;" alt="Afonso Jorge Ramos"/><br /><sub><b>Afonso Jorge Ramos</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=afonsojramos" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://tjenkinson.me/"><img src="https://avatars.githubusercontent.com/u/3259993?v=4?s=100" width="100px;" alt="Tom Jenkinson"/><br /><sub><b>Tom Jenkinson</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=tjenkinson" title="Documentation">📖</a></td>
    </tr>
    <tr>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/phormio"><img src="https://avatars.githubusercontent.com/u/28146332?v=4?s=100" width="100px;" alt="phormio"/><br /><sub><b>phormio</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=phormio" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://buildo.io/"><img src="https://avatars.githubusercontent.com/u/2643520?v=4?s=100" width="100px;" alt="Giovanni Gonzaga"/><br /><sub><b>Giovanni Gonzaga</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=giogonzo" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=giogonzo" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://caurea.org/"><img src="https://avatars.githubusercontent.com/u/34538?v=4?s=100" width="100px;" alt="Tomas Carnecky"/><br /><sub><b>Tomas Carnecky</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=wereHamster" title="Code">💻</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/Djaler"><img src="https://avatars.githubusercontent.com/u/7964583?v=4?s=100" width="100px;" alt="Kirill Romanov"/><br /><sub><b>Kirill Romanov</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=Djaler" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=Djaler" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=Djaler" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://giovannyg.github.io/"><img src="https://avatars.githubusercontent.com/u/5326411?v=4?s=100" width="100px;" alt="Giovanny González"/><br /><sub><b>Giovanny González</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=giovannyg" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/markkulube"><img src="https://avatars.githubusercontent.com/u/34955942?v=4?s=100" width="100px;" alt="Mark Kulube"/><br /><sub><b>Mark Kulube</b></sub></a><br /><a href="#infra-markkulube" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://www.undiscoveredfeatures.com/"><img src="https://avatars.githubusercontent.com/u/354848?v=4?s=100" width="100px;" alt="Peter Hamilton"/><br /><sub><b>Peter Hamilton</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=hamiltop" title="Code">💻</a></td>
    </tr>
    <tr>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/ChineduOzodi"><img src="https://avatars.githubusercontent.com/u/11678369?v=4?s=100" width="100px;" alt="Chinedu Ozodi"/><br /><sub><b>Chinedu Ozodi</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=ChineduOzodi" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/gunar"><img src="https://avatars.githubusercontent.com/u/7684574?v=4?s=100" width="100px;" alt="Gunar Gessner"/><br /><sub><b>Gunar Gessner</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=gunar" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/CSBatchelor"><img src="https://avatars.githubusercontent.com/u/18668440?v=4?s=100" width="100px;" alt="Christian Batchelor"/><br /><sub><b>Christian Batchelor</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=CSBatchelor" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://tomeraberba.ch/"><img src="https://avatars.githubusercontent.com/u/23299544?v=4?s=100" width="100px;" alt="Tomer Aberbach"/><br /><sub><b>Tomer Aberbach</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=TomerAberbach" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=TomerAberbach" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=TomerAberbach" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/0xflotus"><img src="https://avatars.githubusercontent.com/u/26602940?v=4?s=100" width="100px;" alt="0xflotus"/><br /><sub><b>0xflotus</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=0xflotus" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/CodeLenny"><img src="https://avatars.githubusercontent.com/u/9272847?v=4?s=100" width="100px;" alt="Ryan Leonard"/><br /><sub><b>Ryan Leonard</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=CodeLenny" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=CodeLenny" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=CodeLenny" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://blog.bitjson.com/"><img src="https://avatars.githubusercontent.com/u/904007?v=4?s=100" width="100px;" alt="Jason Dreyzehner"/><br /><sub><b>Jason Dreyzehner</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=bitjson" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=bitjson" title="Tests">⚠️</a></td>
    </tr>
    <tr>
      <td align="center" valign="top" width="14.28%"><a href="https://matinzd.dev/"><img src="https://avatars.githubusercontent.com/u/24797481?v=4?s=100" width="100px;" alt="Matin Zadeh Dolatabad"/><br /><sub><b>Matin Zadeh Dolatabad</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=matinzd" title="Code">💻</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://goo.gl/IlWG8U"><img src="https://avatars.githubusercontent.com/u/500?v=4?s=100" width="100px;" alt="Juan Julián Merelo Guervós"/><br /><sub><b>Juan Julián Merelo Guervós</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=JJ" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/SimenB"><img src="https://avatars.githubusercontent.com/u/1404810?v=4?s=100" width="100px;" alt="Simen Bekkhus"/><br /><sub><b>Simen Bekkhus</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=SimenB" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/tskj"><img src="https://avatars.githubusercontent.com/u/25415972?v=4?s=100" width="100px;" alt="Tarjei Skjærset"/><br /><sub><b>Tarjei Skjærset</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=tskj" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://denisgorbachev.com/"><img src="https://avatars.githubusercontent.com/u/829578?v=4?s=100" width="100px;" alt="Denis Gorbachev"/><br /><sub><b>Denis Gorbachev</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=DenisGorbachev" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://senocular.github.io/"><img src="https://avatars.githubusercontent.com/u/3536716?v=4?s=100" width="100px;" alt="Trevor McCauley"/><br /><sub><b>Trevor McCauley</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=senocular" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://grantkiely.com/"><img src="https://avatars.githubusercontent.com/u/1948935?v=4?s=100" width="100px;" alt="Grant Kiely"/><br /><sub><b>Grant Kiely</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=gkiely" title="Documentation">📖</a></td>
    </tr>
    <tr>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/vecerek"><img src="https://avatars.githubusercontent.com/u/5737996?v=4?s=100" width="100px;" alt="Attila Večerek"/><br /><sub><b>Attila Večerek</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=vecerek" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=vecerek" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=vecerek" title="Tests">⚠️</a></td>
      <td align="center" valign="top" width="14.28%"><a href="http://www.zachbjornson.com/"><img src="https://avatars.githubusercontent.com/u/469365?v=4?s=100" width="100px;" alt="Zach Bjornson"/><br /><sub><b>Zach Bjornson</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=zbjornson" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=zbjornson" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/bennettp123"><img src="https://avatars.githubusercontent.com/u/1610227?v=4?s=100" width="100px;" alt="Bennett Perkins"/><br /><sub><b>Bennett Perkins</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=bennettp123" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/nielk"><img src="https://avatars.githubusercontent.com/u/4980521?v=4?s=100" width="100px;" alt="Alexandre Oger"/><br /><sub><b>Alexandre Oger</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=nielk" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=nielk" title="Code">💻</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/ej-shafran"><img src="https://avatars.githubusercontent.com/u/116496520?v=4?s=100" width="100px;" alt="ej shafran"/><br /><sub><b>ej shafran</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=ej-shafran" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/gruhn"><img src="https://avatars.githubusercontent.com/u/26570572?v=4?s=100" width="100px;" alt="Niklas Gruhn"/><br /><sub><b>Niklas Gruhn</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=gruhn" title="Code">💻</a> <a href="#question-gruhn" title="Answering Questions">💬</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://patrickroza.com/"><img src="https://avatars.githubusercontent.com/u/42661?v=4?s=100" width="100px;" alt="Patrick Roza"/><br /><sub><b>Patrick Roza</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=patroza" title="Code">💻</a></td>
    </tr>
    <tr>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/cindywu"><img src="https://avatars.githubusercontent.com/u/1177031?v=4?s=100" width="100px;" alt="Cindy Wu"/><br /><sub><b>Cindy Wu</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=cindywu" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/nmay231"><img src="https://avatars.githubusercontent.com/u/35386821?v=4?s=100" width="100px;" alt="Noah"/><br /><sub><b>Noah</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=nmay231" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/jamesbvaughan"><img src="https://avatars.githubusercontent.com/u/2906913?v=4?s=100" width="100px;" alt="James Vaughan"/><br /><sub><b>James Vaughan</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=jamesbvaughan" title="Documentation">📖</a> <a href="https://github.com/dubzzz/fast-check/commits?author=jamesbvaughan" title="Code">💻</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/AlexErrant"><img src="https://avatars.githubusercontent.com/u/109672176?v=4?s=100" width="100px;" alt="Alex Errant"/><br /><sub><b>Alex Errant</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=AlexErrant" title="Code">💻</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://ahrjarrett.com/"><img src="https://avatars.githubusercontent.com/u/15133992?v=4?s=100" width="100px;" alt="andrew jarrett"/><br /><sub><b>andrew jarrett</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=ahrjarrett" title="Code">💻</a> <a href="https://github.com/dubzzz/fast-check/commits?author=ahrjarrett" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/matthyk"><img src="https://avatars.githubusercontent.com/u/53833818?v=4?s=100" width="100px;" alt="Matthias Keckl"/><br /><sub><b>Matthias Keckl</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=matthyk" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/dmurvihill"><img src="https://avatars.githubusercontent.com/u/1649120?v=4?s=100" width="100px;" alt="Dolan Murvihill"/><br /><sub><b>Dolan Murvihill</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=dmurvihill" title="Code">💻</a></td>
    </tr>
    <tr>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/emilianbold"><img src="https://avatars.githubusercontent.com/u/991554?v=4?s=100" width="100px;" alt="Emi"/><br /><sub><b>Emi</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=emilianbold" title="Code">💻</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://www.russbiggs.com/"><img src="https://avatars.githubusercontent.com/u/8487728?v=4?s=100" width="100px;" alt="Russ Biggs"/><br /><sub><b>Russ Biggs</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=russbiggs" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/adamni21"><img src="https://avatars.githubusercontent.com/u/85580454?v=4?s=100" width="100px;" alt="adamni21"/><br /><sub><b>adamni21</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=adamni21" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/josephjunker"><img src="https://avatars.githubusercontent.com/u/1519098?v=4?s=100" width="100px;" alt="Joseph Junker"/><br /><sub><b>Joseph Junker</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=josephjunker" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/rushelex"><img src="https://avatars.githubusercontent.com/u/41122157?v=4?s=100" width="100px;" alt="Aleksey Shelementev"/><br /><sub><b>Aleksey Shelementev</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=rushelex" title="Code">💻</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/rugk"><img src="https://avatars.githubusercontent.com/u/11966684?v=4?s=100" width="100px;" alt="rugk"/><br /><sub><b>rugk</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=rugk" title="Documentation">📖</a></td>
      <td align="center" valign="top" width="14.28%"><a href="https://github.com/makeeno"><img src="https://avatars.githubusercontent.com/u/90332566?v=4?s=100" width="100px;" alt="Makien Osman"/><br /><sub><b>Makien Osman</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=makeeno" title="Documentation">📖</a></td>
    </tr>
    <tr>
      <td align="center" valign="top" width="14.28%"><a href="https://jneidel.com/"><img src="https://avatars.githubusercontent.com/u/25589715?v=4?s=100" width="100px;" alt="Jonathan Neidel"/><br /><sub><b>Jonathan Neidel</b></sub></a><br /><a href="https://github.com/dubzzz/fast-check/commits?author=jneidel" title="Documentation">📖</a></td>
    </tr>
  </tbody>
</table>

<!-- markdownlint-restore -->
<!-- prettier-ignore-end -->

<!-- ALL-CONTRIBUTORS-LIST:END -->

This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome! [Become one of them](CONTRIBUTING.md)

## Sponsors 💸

Many individuals and companies offer their financial support to the project, a huge thanks to all of them too 💓

<a href="https://github.com/sponsors/dubzzz"><img align="center" src="https://raw.githubusercontent.com/dubzzz/sponsors-svg/main/sponsorkit/sponsors.svg" alt="all sponsors" /></a>

You can also become one of them by contributing via [GitHub Sponsors](https://github.com/sponsors/dubzzz) or [OpenCollective](https://opencollective.com/fast-check/contribute).
