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Setup

We recommend using Vitest, but you're free to use the library with any test runner that's ESM compatible.

Vitest​

  1. Add development dependencies

    npm install --save-dev \
      @testing-library/svelte \
      @testing-library/jest-dom \
      @sveltejs/vite-plugin-svelte \
      vitest \
      jsdom

    Optionally install @vitest/ui, which opens a UI within a browser window to follow the progress and interact with your tests.

    npm install --save-dev @vitest/ui

  2. Add a vitest-setup.js file to optionally set up @testing-library/jest-dom expect matchers.

    vitest-setup.js
    import '@testing-library/jest-dom/vitest'

  3. Add vitest.config.js, or update your existing vite.config.js, with the svelte and svelteTesting Vite plugins. Set the testing environment to your DOM library of choice and optionally configure your setup file from step (2).

    vite.config.js
    import {defineConfig} from 'vitest/config'
    import {svelte} from '@sveltejs/vite-plugin-svelte'
    import {svelteTesting} from '@testing-library/svelte/vite'

    export default defineConfig({
      plugins: [svelte(), svelteTesting()],
      test: {
        environment: 'jsdom',
        setupFiles: ['./vitest-setup.js'],
      },
    })

    Or, if you're using SvelteKit:

    vite.config.js
    import {defineConfig} from 'vitest/config'
    import {sveltekit} from '@sveltejs/kit/vite'
    import {svelteTesting} from '@testing-library/svelte/vite'

    export default defineConfig({
      plugins: [sveltekit(), svelteTesting()],
      test: {
        environment: 'jsdom',
        setupFiles: ['./vitest-setup.js'],
      },
    })
    note

    The svelteTesting plugin:

    If needed, you can disable either behavior. Disabling both options is equivalent to omitting the plugin.

    svelteTesting({
      // disable auto cleanup
      autoCleanup: false,
      // disable browser resolution condition
      resolveBrowser: false,
    })

    Resolving the browser condition may cause issues if you have a complex Vite configuration or dependencies that cannot be loaded into Node.js. See testing-library/svelte-testing-library#222 for more information and alternative configuration options to ensure Svelte's browser code is used.

  4. Add test scripts to your package.json to run the tests with Vitest

    package.json
    {
      "scripts": {
        "test": "vitest run",
        "test:ui": "vitest --ui",
        "test:watch": "vitest"
      }
    }

  5. 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 test

Jest​

@testing-library/svelte is ESM-only, which means you must use Jest in ESM mode.

  1. Add development dependencies

    npm install --save-dev \
      @testing-library/svelte \
      @testing-library/jest-dom \
      svelte-jester \
      jest \
      jest-environment-jsdom

  2. Add a jest-setup.js file to configure @testing-library/jest-dom, if using.

    jest-setup.js
    import '@testing-library/jest-dom'

  3. Configure Jest to use jsdom, transform Svelte files, and use your setup file

    jest.config.js
    module.exports = {
      transform: {
        '^.+\\.svelte$': 'svelte-jester',
      },
      moduleFileExtensions: ['js', 'svelte'],
      extensionsToTreatAsEsm: ['.svelte'],
      testEnvironment: 'jsdom',
      setupFilesAfterEnv: ['<rootDir>/jest-setup.js'],
    }

  4. Add the following to your package.json

    package.json
    {
      "scripts": {
        "test": "npx --node-options=\"--experimental-vm-modules\" jest src",
        "test:watch": "npx --node-options=\"--experimental-vm-modules\" jest src --watch"
      }
    }

  5. Create your component + test file (checkout the rest of the docs to see how) and run it

    npm test

TypeScript and preprocessors​

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

If you'd like include any other Svelte preprocessors, see the svelte-jester docs.