Setup

We recommend using Jest but you're free to use the library with any testing framework and runner you're comfortable with.

Jest

Install Jest & jest-environment-jsdom

npm install --save-dev jest jest-environment-jsdom

Add the following to your package.json

{
  "scripts": {
    "test": "jest src",
    "test:watch": "npm run test -- --watch"
  }
}

You'll need to compile the Svelte components before using them in Jest, so we need to install svelte-jester
```
npm install --save-dev svelte-jester
```

Add the following Jest configuration to your package.json

{
  "jest": {
    "transform": {
      "^.+\\.svelte$": "svelte-jester"
    },
    "moduleFileExtensions": ["js", "svelte"],
    "testEnvironment": "jsdom"
  }
}

If you are using ES6 modules in your project you have to add Jest's babel transform setting (it is set by default, but since we are overriding the transform config, we have to add it explicitly)
5.1 Install babel-jest
```
npm install --save-dev babel-jest
```
5.2. Add a basic .babelrc configuration
```
{
  "presets": [["@babel/preset-env", {"targets": {"node": "current"}}]]
}
```
5.3. Update the Jest transform configuration
```
"transform": {
  "^.+\\.js$": "babel-jest",
  "^.+\\.svelte$": "svelte-jester"
},
```
This is optional but it is recommended, you can install jest-dom to add handy assertions to Jest
6.1 Install jest-dom
```
npm install --save-dev @testing-library/jest-dom
```
6.2 Add the following to your Jest configuration in package.json
```
{
  "setupFilesAfterEnv": ["@testing-library/jest-dom/extend-expect"]
}
```
Create your component + test file (checkout the rest of the docs to see how) and run it
```
npm run test
```

Vitest

Install Vitest and jsdom
```
npm install --save-dev vitest jsdom
```

Add the following to your package.json

{
  "scripts": {
    "test": "vitest run src",
    "test:watch": "vitest src"
  }
}

You'll need to compile the Svelte components before using them in Vitest, so you need to install @sveltejs/vite-plugin-svelte and Vite
```
npm install --save-dev @sveltejs/vite-plugin-svelte vite
```

Add a vitest.config.ts configuration file to the root of your project

import {defineConfig} from 'vite'
import {svelte} from '@sveltejs/vite-plugin-svelte'

export default defineConfig({
  plugins: [svelte({hot: !process.env.VITEST})],
  test: {
    include: ['src/**/*.{test,spec}.{js,mjs,cjs,ts,mts,cts,jsx,tsx}'],
    globals: true,
    environment: 'jsdom',
  },
})

This is optional but it is recommended, you can install jest-dom to add handy assertions to Jest
5.1 Install jest-dom
```
npm install --save-dev @testing-library/jest-dom
```
5.2 import @testing-library/jest-dom at the start of your test files
```
import '@testing-library/jest-dom'
```
Create your component and a test file (checkout the rest of the docs to see how) and run the following command to run the tests.
```
npm run test
```

Typescript

To use Typescript, you'll need to install and configure svelte-preprocess and ts-jest. For full instructions, see the svelte-jester docs.

Preprocessors

If you'd like to also include any Svelte preprocessors then simply follow the instructions over at svelte-jester.

Jest​

Vitest​

Typescript​

Preprocessors​

Jest

Vitest

Typescript

Preprocessors