https://github.com/lukemorales/jest-type-matchers

Custom jest matchers to test the state of your types
https://github.com/lukemorales/jest-type-matchers

assertions custom-jest-matcher custom-matcher extend jest jest-matchers matchers test testing type-assertions type-testing types typescript

Last synced: 12 days ago
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Custom jest matchers to test the state of your types

• Host: GitHub
• URL: https://github.com/lukemorales/jest-type-matchers
• Owner: lukemorales
• License: mit
• Created: 2022-10-08T18:31:05.000Z (about 2 years ago)
• Default Branch: main
• Last Pushed: 2022-10-10T02:24:46.000Z (about 2 years ago)
• Last Synced: 2024-12-04T20:53:59.643Z (17 days ago)
• Topics: assertions, custom-jest-matcher, custom-matcher, extend, jest, jest-matchers, matchers, test, testing, type-assertions, type-testing, types, typescript
• Language: TypeScript
• Homepage: https://www.npmjs.com/package/@lukemorales/jest-type-matchers
• Size: 115 KB
• Stars: 7
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE.md

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README

        


  



jest-type-matchers




  

  

  

  

  

  

  

  





  Custom jest matchers to test the state of your types.





  You write Typescript and want assert various things about the state of your types?
This library provides a set of custom matchers that you can use to extend jest
and assert your test results against expected types.



## 📦 Install

This library is available as a package on NPM, install with your favorite package manager:

```dircolors

npm install --save-dev @lukemorales/jest-type-matchers

```

## ⚡ Quick start

Import `@lukemorales/jest-type-matchers` once in your [tests setup

file](

  https://jestjs.io/docs/en/configuration.html#setupfilesafterenv-array):

```ts

// In your jest-setup.ts (or any other name)

import '@lukemorales/jest-type-matchers';

// In jest.config.js add (if you haven't already)

setupFilesAfterEnv: ['/jest-setup.ts']

```

### Custom Matchers

These custom matchers allow you to just check your types. This means that they will **never** fail your test suite because type-checking happens at compile-time only.

#### `toHaveType`

```ts

expect(true).toHaveType();

type Result = { ok: boolean } & { data: null };

expect({ ok: true, data: null }).toHaveType<{ ok: boolean; data: null }>();

```

This allows you to check that a variable has an expected type.

#### `toNotHaveType`

```ts

expect('hello world').toNotHaveType();

```

This allows you to check that a variable does not have a specific type.

#### `toHaveStrictType`

```ts

expect(true).toHaveStrictType();

type Result = { ok: boolean } & { data: null };

expect({ ok: true, data: null }).toHaveStrictType<{ ok: boolean } & { data: null }>();

```

This allows you to check that a variable is strict equal to an expected type.

#### `toNotHaveStrictType`

```ts

expect('hello world').toNotHaveStrictType();

```

This allows you to check that a variable is not strict equal to a specific type.