Test runner

Storybook test runner turns all of your stories into executable tests. It is powered by Jest and Playwright.

• For those without a play function: it verifies whether the story renders without any errors.
• For those with a play function: it also checks for errors in the play function and that all assertions passed.

These tests run in a live browser and can be executed via the command line or your CI server.

Setup

The test-runner is a standalone, framework-agnostic utility that runs parallel to your Storybook. You will need to take some additional steps to set it up properly. Detailed below is our recommendation to configure and execute it.

Run the following command to install it.

npm install @storybook/test-runner --save-dev

Update your package.json scripts and enable the test runner.

{
  "scripts": {
    "test-storybook": "test-storybook"
  }
}

Start your Storybook with:

npm run storybook

Finally, open a new terminal window and run the test-runner with:

npm run test-storybook

Configure

Test runner offers zero-config support for Storybook. However, you can run test-storybook --eject for more fine-grained control. It generates a test-runner-jest.config.js file at the root of your project, which you can modify. Additionally, you can extend the generated configuration file and provide testEnvironmentOptions as the test runner also uses jest-playwright under the hood.

CLI Options

The test-runner is powered by Jest and accepts a subset of its CLI options (for example, --watch, --maxWorkers). If you're already using any of those flags in your project, you should be able to migrate them into Storybook's test-runner without any issues. Listed below are all the available flags and examples of using them.

npm run test-storybook -- --watch

Run tests against a deployed Storybook

By default, the test-runner assumes that you're running it against a locally served Storybook on port 6006. If you want to define a target URL to run against deployed Storybooks, you can use the --url flag:

npm run test-storybook -- --url https://the-storybook-url-here.com

Alternatively, you can set the TARGET_URL environment variable and run the test-runner:

TARGET_URL=https://the-storybook-url-here.com yarn test-storybook

Set up CI to run tests

You can also configure the test-runner to run tests on a CI environment. Documented below are some recipes to help you get started.

Run against deployed Storybooks via Github Actions deployment

If you're publishing your Storybook with services such as Vercel or Netlify, they emit a deployment_status event in GitHub Actions. You can use it and set the deployment_status.target_url as the TARGET_URL environment variable. Here's how:

name: Storybook Tests
 
on: deployment_status
 
jobs:
  test:
    timeout-minutes: 60
    runs-on: ubuntu-latest
    if: github.event.deployment_status.state == 'success'
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version-file: '.nvmrc'
      - name: Install dependencies
        run: yarn
      - name: Install Playwright
        run: npx playwright install --with-deps
      - name: Run Storybook tests
        run: yarn test-storybook
        env:
          TARGET_URL: '${{ github.event.deployment_status.target_url }}'

Run against non-deployed Storybooks

You can use your CI provider (for example, GitHub Actions, GitLab Pipelines, CircleCI) to build and run the test runner against your built Storybook. Here's a recipe that relies on third-party libraries, that is to say, concurrently, http-server, and wait-on to build Storybook and run tests with the test-runner.

name: 'Storybook Tests'
 
on: push
 
jobs:
  test:
    timeout-minutes: 60
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version-file: '.nvmrc'
      - name: Install dependencies
        run: yarn
      - name: Install Playwright
        run: npx playwright install --with-deps
      - name: Build Storybook
        run: yarn build-storybook --quiet
      - name: Serve Storybook and run tests
        run: |
          npx concurrently -k -s first -n "SB,TEST" -c "magenta,blue" \
            "npx http-server storybook-static --port 6006 --silent" \
            "npx wait-on tcp:127.0.0.1:6006 && yarn test-storybook"

What's the difference between Chromatic and Test runner?

The test-runner is a generic testing tool that can run locally or on CI and be configured or extended to run all kinds of tests.

Chromatic is a cloud-based service that runs visual and component tests (and soon accessibility tests) without setting up the test runner. It also syncs with your git provider and manages access control for private projects.

However, you might want to pair the test runner and Chromatic in some cases.

• Use it locally and Chromatic on your CI.
• Use Chromatic for visual and component tests and run other custom tests using the test runner.

Advanced configuration

Test hook API

The test-runner renders a story and executes its play function if one exists. However, certain behaviors are impossible to achieve via the play function, which executes in the browser. For example, if you want the test-runner to take visual snapshots for you, this is possible via Playwright/Jest but must be executed in Node.

The test-runner exports test hooks that can be overridden globally to enable use cases like visual or DOM snapshots. These hooks give you access to the test lifecycle before and after the story is rendered. Listed below are the available hooks and an overview of how to use them.

To enable the hooks API, you'll need to add a new configuration file inside your Storybook directory and set them up as follows:

import type { TestRunnerConfig } from '@storybook/test-runner';
 
const config: TestRunnerConfig = {
  // Hook that is executed before the test runner starts running tests
  setup() {
    // Add your configuration here.
  },
  /* Hook to execute before a story is initially visited before being rendered in the browser.
   * The page argument is the Playwright's page object for the story.
   * The context argument is a Storybook object containing the story's id, title, and name.
   */
  async preVisit(page, context) {
    // Add your configuration here.
  },
  /* Hook to execute after a story is visited and fully rendered.
   * The page argument is the Playwright's page object for the story
   * The context argument is a Storybook object containing the story's id, title, and name.
   */
  async postVisit(page, context) {
    // Add your configuration here.
  },
};
 
export default config;

When the test-runner executes, your existing tests will go through the following lifecycle:

• The setup function is executed before all the tests run.
• The context object is generated containing the required information.
• Playwright navigates to the story's page.
• The preVisit function is executed.
• The story is rendered, and any existing play functions are executed.
• The postVisit function is executed.

(Experimental) Filter tests

When you run the test-runner on Storybook, it tests every story by default. However, if you want to filter the tests, you can use the tags configuration option. Storybook originally introduced this feature to generate automatic documentation for stories. But it can be further extended to configure the test-runner to run tests according to the provided tags using a similar configuration option or via CLI flags (e.g., --includeTags, --excludeTags, --skipTags), only available with the latest stable release (0.15 or higher). Listed below are the available options and an overview of how to use them.

import type { TestRunnerConfig } from '@storybook/test-runner';
 
const config: TestRunnerConfig = {
  tags: {
    include: ['test-only', 'pages'],
    exclude: ['no-tests', 'tokens'],
    skip: ['skip-test', 'layout'],
  },
};
 
export default config;

Disabling tests

If you want to prevent specific stories from being tested by the test-runner, you can configure your story with a custom tag, enable it to the test-runner configuration file or run the test-runner with the --excludeTags CLI flag and exclude them from testing. This is helpful when you want to exclude stories that are not yet ready for testing or are irrelevant to your tests. For example:

// Replace your-framework with the name of your framework
import type { Meta, StoryObj } from '@storybook/your-framework';
 
import { MyComponent } from './MyComponent';
 
const meta: Meta<typeof MyComponent> = {
  component: MyComponent,
  tags: ['no-tests'], // 👈 Provides the `no-tests` tag to all stories in this file
};
 
export default meta;
type Story = StoryObj<typeof MyComponent>;
 
export const ExcludeStory: Story = {
  //👇 Adds the `no-tests` tag to this story to exclude it from the tests when enabled in the test-runner configuration
  tags: ['no-tests'],
};

Run tests for a subset of stories

To allow the test-runner only to run tests on a specific story or subset of stories, you can configure the story with a custom tag, enable it in the test-runner configuration file or run the test-runner with the --includeTags CLI flag and include them in your tests. For example, if you wanted to run tests based on the test-only tag, you can adjust your configuration as follows:

// Replace your-framework with the name of your framework
import type { Meta, StoryObj } from '@storybook/your-framework';
 
import { MyComponent } from './MyComponent';
 
const meta: Meta<typeof MyComponent> = {
  component: MyComponent,
  tags: ['test-only'], // 👈 Provides the `test-only` tag to all stories in this file
};
 
export default meta;
type Story = StoryObj<typeof MyComponent>;
 
export const IncludeStory: Story = {
  //👇 Adds the `test-only` tag to this story to be included in the tests when enabled in the test-runner configuration
  tags: ['test-only'],
};

Skip tests

If you want to skip running tests on a particular story or subset of stories, you can configure your story with a custom tag, enable it in the test-runner configuration file, or run the test-runner with the --skipTags CLI flag. Running tests with this option will cause the test-runner to ignore and flag them accordingly in the test results, indicating that the tests are temporarily disabled. For example:

// Replace your-framework with the name of your framework
import type { Meta, StoryObj } from '@storybook/your-framework';
 
import { MyComponent } from './MyComponent';
 
const meta: Meta<typeof MyComponent> = {
  component: MyComponent,
  tags: ['skip-test'], // 👈 Provides the `skip-test` tag to all stories in this file
};
 
export default meta;
type Story = StoryObj<typeof MyComponent>;
 
export const SkipStory: Story = {
  //👇 Adds the `skip-test` tag to this story to allow it to be skipped in the tests when enabled in the test-runner configuration
  tags: ['skip-test'],
};

Authentication for deployed Storybooks

If you use a secure hosting provider that requires authentication to host your Storybook, you may need to set HTTP headers. This is mainly because of how the test runner checks the status of the instance and the index of its stories through fetch requests and Playwright. To do this, you can modify the test-runner configuration file to include the getHttpHeaders function. This function takes the URL of the fetch calls and page visits as input and returns an object containing the headers that need to be set.

import type { TestRunnerConfig } from '@storybook/test-runner';
 
const config: TestRunnerConfig = {
  getHttpHeaders: async (url) => {
    const token = url.includes('prod') ? 'prod-token' : 'dev-token';
    return {
      Authorization: `Bearer ${token}`,
    };
  },
};
 
export default config;

Helpers

The test-runner exports a few helpers that can be used to make your tests more readable and maintainable by accessing Storybook's internals (e.g., args, parameters). Listed below are the available helpers and an overview of how to use them.

import type { TestRunnerConfig } from '@storybook/test-runner';
import { getStoryContext, waitForPageReady } from '@storybook/test-runner';
 
const config: TestRunnerConfig = {
  // Hook that is executed before the test runner starts running tests
  setup() {
    // Add your configuration here.
  },
  /* Hook to execute before a story is initially visited before being rendered in the browser.
   * The page argument is the Playwright's page object for the story.
   * The context argument is a Storybook object containing the story's id, title, and name.
   */
  async preVisit(page, context) {
    // Add your configuration here.
  },
  /* Hook to execute after a story is visited and fully rendered.
   * The page argument is the Playwright's page object for the story
   * The context argument is a Storybook object containing the story's id, title, and name.
   */
  async postVisit(page, context) {
    // Get the entire context of a story, including parameters, args, argTypes, etc.
    const storyContext = await getStoryContext(page, context);
 
    // This utility function is designed for image snapshot testing. It will wait for the page to be fully loaded, including all the async items (e.g., images, fonts, etc.).
    await waitForPageReady(page);
 
    // Add your configuration here.
  },
};
 
export default config;

Accessing story information with the test-runner

If you need to access information about the story, such as its parameters, the test-runner includes a helper function named getStoryContext that you can use to retrieve it. You can then use it to customize your tests further as needed. For example, if you need to configure Playwright's page viewport size to use the viewport size defined in the story's parameters, you can do so as follows:

import type { TestRunnerConfig } from '@storybook/test-runner';
import { getStoryContext } from '@storybook/test-runner';
 
const { MINIMAL_VIEWPORTS } = require('@storybook/addon-viewport');
 
const DEFAULT_VIEWPORT_SIZE = { width: 1280, height: 720 };
 
const config: TestRunnerConfig = {
  async preVisit(page, story) {
    // Accesses the story's parameters and retrieves the viewport used to render it
    const context = await getStoryContext(page, story);
    const viewportName = context.parameters?.viewport?.defaultViewport;
    const viewportParameter = MINIMAL_VIEWPORTS[viewportName];
 
    if (viewportParameter) {
      const viewportSize = Object.entries(viewportParameter.styles).reduce(
        (acc, [screen, size]) => ({
          ...acc,
          // Converts the viewport size from percentages to numbers
          [screen]: parseInt(size),
        }),
        {}
      );
      // Configures the Playwright page to use the viewport size
      page.setViewportSize(viewportSize);
    } else {
      page.setViewportSize(DEFAULT_VIEWPORT_SIZE);
    }
  },
};
 
export default config;

Working with assets

If you're running a specific set of tests (e.g., image snapshot testing), the test-runner provides a helper function named waitForPageReady that you can use to ensure the page is fully loaded and ready before running the test. For example:

import type { TestRunnerConfig } from '@storybook/test-runner';
 
import { waitForPageReady } from '@storybook/test-runner';
 
import { toMatchImageSnapshot } from 'jest-image-snapshot';
 
const customSnapshotsDir = `${process.cwd()}/__snapshots__`;
 
const config: TestRunnerConfig = {
  setup() {
    expect.extend({ toMatchImageSnapshot });
  },
  async postVisit(page, context) {
    // Awaits for the page to be loaded and available including assets (e.g., fonts)
    await waitForPageReady(page);
 
    // Generates a snapshot file based on the story identifier
    const image = await page.screenshot();
    expect(image).toMatchImageSnapshot({
      customSnapshotsDir,
      customSnapshotIdentifier: context.id,
    });
  },
};
 
export default config;

Index.json mode

The test-runner transforms your story files into tests when testing a local Storybook. For a remote Storybook, it uses the Storybook's index.json (formerly stories.json) file (a static index of all the stories) to run the tests.

Why?

Suppose you run into a situation where the local and remote Storybooks appear out of sync, or you might not even have access to the code. In that case, the index.json file is guaranteed to be the most accurate representation of the deployed Storybook you are testing. To test a local Storybook using this feature, use the --index-json flag as follows:

npm run test-storybook -- --index-json

If you need to disable it, use the --no-index-json flag:

npm run test-storybook -- --no-index-json

How do I check if my Storybook has a index.json file?

Index.json mode requires a index.json file. Open a browser window and navigate to your deployed Storybook instance (for example, https://your-storybook-url-here.com/index.json). You should see a JSON file that starts with a "v": 3 key, immediately followed by another key called "stories", which contains a map of story IDs to JSON objects. If that is the case, your Storybook supports index.json mode.

Troubleshooting

The test runner seems flaky and keeps timing out

If your tests time out with the following message:

Timeout - Async callback was not invoked within the 15000 ms timeout specified by jest.setTimeout

It might be that Playwright couldn't handle testing the number of stories you have in your project. Perhaps you have a large number of stories, or your CI environment has a really low RAM configuration. In such cases, you should limit the number of workers that run in parallel by adjusting your command as follows:

{
  "scripts": {
    "test-storybook:ci": "yarn test-storybook --maxWorkers=2"
  }
}

The error output in the CLI is too short

By default, the test runner truncates error outputs at 1000 characters, and you can check the full output directly in Storybook in the browser. However, if you want to change that limit, you can do so by setting the DEBUG_PRINT_LIMIT environment variable to a number of your choosing, for example, DEBUG_PRINT_LIMIT=5000 yarn test-storybook.

Run the test runner in other CI environments

As the test runner is based on Playwright, you might need to use specific docker images or other configurations depending on your CI setup. In that case, you can refer to the Playwright CI docs for more information.

Tests filtered by tags are incorrectly executed

If you've enabled filtering tests with tags and provided similar tags to the include and exclude lists, the test-runner will execute the tests based on the exclude list and ignore the include list. To avoid this, make sure the tags provided to the include and exclude lists differ.

The test runner doesn't support Yarn PnP out of the box

If you've enabled the test-runner in a project running on a newer version of Yarn with Plug'n'Play (PnP) enabled, the test-runner might not work as expected and may generate the following error when running tests:

PlaywrightError: jest-playwright-preset: Cannot find playwright package to use chromium

This is due to the test-runner using the community-maintained package jest-playwright-preset that still needs to support this feature. To solve this, you can either switch the nodeLinker setting to node-modules or install Playwright as a direct dependency in your project, followed by adding the browser binaries via the install command.

Learn about other UI tests

• Component tests for user behavior simulation
• Visual tests for appearance
• Accessibility tests for accessibility
• Snapshot tests for rendering errors and warnings
• Test runner to automate test execution
• Test coverage for measuring code coverage
• End-to-end tests for simulating real user scenarios
• Unit tests for functionality