National Preventative Mechanism

    @storybook/addon-storyshots-puppeteer
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    6.3.6 • Public • Published

    StoryShots + Puppeteer

    Getting Started

    Add the following modules into your app.

    npm install @storybook/addon-storyshots-puppeteer puppeteer --save-dev

    ⚠️ As of Storybook 5.3 puppeteer is no more included in addon dependencies and must be added to your project directly.

    Configure Storyshots for Puppeteer tests

    ⚠️ React-native is not supported by this test function.

    When willing to run Puppeteer tests for your stories, you have two options:

    • Have a storybook running (ie. accessible via http(s), for instance using npm run storybook)
    • Have a static build of the storybook (for instance, using npm run build-storybook)

    Then you will need to reference the storybook URL (file://... if local, http(s)://... if served)

    puppeteerTest

    Allows to define arbitrary Puppeteer tests as story.parameters.puppeteerTest function.

    You can either create a new Storyshots instance or edit the one you previously used:

    import initStoryshots from '@storybook/addon-storyshots';
    import { puppeteerTest } from '@storybook/addon-storyshots-puppeteer';
    
    initStoryshots({ suite: 'Puppeteer storyshots', test: puppeteerTest() });

    Then, in your stories:

    export const myExample = () => {
      ...
    };
    myExample.parameters = {
      async puppeteerTest(page) {
        const element = await page.$('<some-selector>');
        await element.click();
        expect(something).toBe(something);
      },
    };

    This will assume you have a storybook running on at http://localhost:6006. Internally here are the steps:

    Specifying the storybook URL

    If you want to set specific storybook URL, you can specify via the storybookUrl parameter, see below:

    import initStoryshots from '@storybook/addon-storyshots';
    import { puppeteerTest } from '@storybook/addon-storyshots-puppeteer';
    
    initStoryshots({
      suite: 'Puppeteer storyshots',
      test: puppeteerTest({ storybookUrl: 'http://my-specific-domain.com:9010' }),
    });

    The above config will use https://my-specific-domain.com:9010 for tests. You can also use query parameters in your URL (e.g. for setting a different background for your storyshots, if you use @storybook/addon-backgrounds).

    You may also use a local static build of storybook if you do not want to run the webpack dev-server:

    import initStoryshots from '@storybook/addon-storyshots';
    import { puppeteerTest } from '@storybook/addon-storyshots-puppeteer';
    
    initStoryshots({
      suite: 'Puppeteer storyshots',
      test: puppeteerTest({
        storybookUrl: 'file:///path/to/my/storybook-static',
        // storybookUrl: 'file://${path.resolve(__dirname, '../storybook-static')}'
      }),
    });

    Specifying options to goto() (Puppeteer API)

    You might use getGotoOptions to specify options when the storybook is navigating to a story (using the goto method). Will be passed to Puppeteer .goto() fn

    import initStoryshots from '@storybook/addon-storyshots';
    import { puppeteerTest } from '@storybook/addon-storyshots-puppeteer';
    
    const getGotoOptions = ({ context, url }) => {
      return {
        waitUntil: 'networkidle0',
      };
    };
    
    initStoryshots({
      suite: 'Puppeteer storyshots',
      test: puppeteerTest({ storybookUrl: 'http://localhost:6006', getGotoOptions }),
    });

    Specifying custom Chrome executable path (Puppeteer API)

    You might use chromeExecutablePath to specify the path to a different version of Chrome, without downloading Chromium. Will be passed to Runs a bundled version of Chromium

    import initStoryshots from '@storybook/addon-storyshots';
    import { puppeteerTest } from '@storybook/addon-storyshots-puppeteer';
    
    const chromeExecutablePath = '/usr/local/bin/chrome';
    
    initStoryshots({
      suite: 'Puppeteer storyshots',
      test: puppeteerTest({ storybookUrl: 'http://localhost:6006', chromeExecutablePath }),
    });

    Specifying a custom Puppeteer browser instance

    You might use the async getCustomBrowser function to obtain a custom instance of a Puppeteer browser object. This will prevent storyshots-puppeteer from creating its own browser. It will create and close pages within the browser, and it is your responsibility to manage the lifecycle of the browser itself.

    import initStoryshots from '@storybook/addon-storyshots';
    import { puppeteerTest } from '@storybook/addon-storyshots-puppeteer';
    import puppeteer from 'puppeteer';
    
    (async function () {
      initStoryshots({
        suite: 'Puppeteer storyshots',
        test: puppeteerTest({
          storybookUrl: 'http://localhost:6006',
          getCustomBrowser: () => puppeteer.connect({ browserWSEndpoint: 'ws://yourUrl' }),
        }),
      });
    })();

    Customizing a page instance

    Sometimes, there is a need to customize a page before it calls the goto api.

    An example of device emulation:

    import initStoryshots from '@storybook/addon-storyshots';
    import { puppeteerTest } from '@storybook/addon-storyshots-puppeteer';
    const devices = require('puppeteer/DeviceDescriptors');
    
    const iPhone = devices['iPhone 6'];
    
    function customizePage(page) {
      return page.emulate(iPhone);
    }
    
    initStoryshots({
      suite: 'Puppeteer storyshots',
      test: puppeteerTest({
        storybookUrl: 'http://localhost:6006',
        customizePage,
      }),
    });

    Specifying setup and tests timeout

    By default, @storybook/addon-storyshots-puppeteer uses 15 second timeouts for browser setup and test functions. Those can be customized with setupTimeout and testTimeout parameters.

    Integrate Puppeteer storyshots with regular app

    You may want to use another Jest project to run your Puppeteer storyshots as they require more resources: Chrome and Storybook built/served. You can find a working example of this in the official-storybook example.

    Integrate Puppeteer storyshots with Create React App

    You have two options here, you can either:

    • Add the storyshots configuration inside any of your test.js file. You must ensure you have either a running storybook or a static build available.

    • Create a custom test file using Jest outside of the CRA scope:

      A more robust approach would be to separate existing test files ran by create-react-app (anything (test|spec).js suffixed files) from the test files to run Puppeteer storyshots. This use case can be achieved by using a custom name for the test file, ie something like puppeteer-storyshots.runner.js. This file will contain the initStoryshots call with Puppeteer storyshots configuration. Then you will create a separate script entry in your package.json, for instance

      {
        "scripts": {
          "puppeteer-storyshots": "jest puppeteer-storyshots.runner.js --config path/to/custom/jest.config.json"
        }
      }

      Note that you will certainly need a custom config file for Jest as you run it outside of the CRA scope and thus you do not have the built-in config.

      Once that's setup, you can run npm run puppeteer-storyshots.

    Reminder

    Puppeteer launches a web browser (Chrome) internally.

    The browser opens a page (either using the static build of storybook or a running instance of Storybook)

    If you run your test without either the static build or a running instance, this wont work.

    To make sure your tests run against the latest changes of your Storybook, you must keep your static build or running Storybook up-to-date. This can be achieved by adding a step before running the test ie: npm run build-storybook && npm run image-snapshots. If you run the Puppeteer storyshots against a running Storybook in dev mode, you don't have to worry about the stories being up-to-date because the dev-server is watching changes and rebuilds automatically.

    axeTest

    Runs Axe accessibility checks and verifies that they pass using jest-puppeteer-axe.

    import initStoryshots from '@storybook/addon-storyshots';
    import { axeTest } from '@storybook/addon-storyshots-puppeteer';
    
    initStoryshots({ suite: 'A11y checks', test: axeTest() });

    For configuration, it uses the same story.parameters.a11y parameter as @storybook/addon-a11y

    Specifying options to axeTest

    import initStoryshots from '@storybook/addon-storyshots';
    import { axeTest } from '@storybook/addon-storyshots-puppeteer';
    
    const beforeAxeTest = (page, { context: { kind, story }, url }) => {
      return new Promise((resolve) =>
        setTimeout(() => {
          resolve();
        }, 600)
      );
    };
    
    initStoryshots({ suite: 'A11y checks', test: axeTest({ beforeAxeTest }) });

    beforeAxeTest receives the Puppeteer page instance and an object: { context: {kind, story}, url}. kind is the kind of the story and the story its name. url is the URL the browser will use to screenshot. beforeAxeTest is part of the promise chain and is called after the browser navigation is completed but before the screenshot is taken. It allows for triggering events on the page elements and delaying the axe test .

    imageSnapshots

    Generates and compares screenshots of your stories using jest-image-snapshot.

    import initStoryshots from '@storybook/addon-storyshots';
    import { imageSnapshot } from '@storybook/addon-storyshots-puppeteer';
    
    initStoryshots({ suite: 'Image storyshots', test: imageSnapshot() });

    It saves all images under __image_snapshots__ folder.

    Specifying options to jest-image-snapshots

    If you wish to customize jest-image-snapshot, then you can provide a getMatchOptions parameter that should return the options config object. Additionally, you can provide beforeScreenshot which is called before the screenshot is captured and a afterScreenshot handler which is called after the screenshot and receives the just created image.

    import initStoryshots from '@storybook/addon-storyshots';
    import { imageSnapshot } from '@storybook/addon-storyshots-puppeteer';
    const getMatchOptions = ({ context: { kind, story }, url }) => {
      return {
        failureThreshold: 0.2,
        failureThresholdType: 'percent',
      };
    };
    const beforeScreenshot = (page, { context: { kind, story }, url }) => {
      return new Promise((resolve) =>
        setTimeout(() => {
          resolve();
        }, 600)
      );
    };
    const afterScreenshot = ({ image, context }) => {
      return new Promise((resolve) =>
        setTimeout(() => {
          resolve();
        }, 600)
      );
    };
    initStoryshots({
      suite: 'Image storyshots',
      test: imageSnapshot({
        storybookUrl: 'http://localhost:6006',
        getMatchOptions,
        beforeScreenshot,
        afterScreenshot,
      }),
    });

    getMatchOptions receives an object: { context: {kind, story}, url}. kind is the kind of the story and the story its name. url is the URL the browser will use to screenshot.

    beforeScreenshot receives the Puppeteer page instance and an object: { context: {kind, story}, url}. kind is the kind of the story and the story its name. url is the URL the browser will use to screenshot. beforeScreenshot is part of the promise chain and is called after the browser navigation is completed but before the screenshot is taken. It allows for triggering events on the page elements and delaying the screenshot and can be used avoid regressions due to mounting animations.

    afterScreenshot receives the created image from puppeteer.

    Specifying options to screenshot() (Puppeteer API)

    You might use getScreenshotOptions to specify options for screenshot. Will be passed to Puppeteer .screenshot() fn

    import initStoryshots from '@storybook/addon-storyshots';
    import { imageSnapshot } from '@storybook/addon-storyshots-puppeteer';
    const getScreenshotOptions = ({ context, url }) => {
      return {
        encoding: 'base64', // encoding: 'base64' is a property required by puppeteer
        fullPage: false, // Do not take the full page screenshot. Default is 'true' in Storyshots.,
      };
    };
    initStoryshots({
      suite: 'Image storyshots',
      test: imageSnapshot({ storybookUrl: 'http://localhost:6006', getScreenshotOptions }),
    });

    getScreenshotOptions receives an object { context: {kind, story}, url}. kind is the kind of the story and the story its name. url is the URL the browser will use to screenshot.

    To create a screenshot of just a single element (with its children), rather than the page or current viewport, an ElementHandle can be returned from beforeScreenshot:

    import initStoryshots from '@storybook/addon-storyshots';
    import { imageSnapshot } from '@storybook/addon-storyshots-puppeteer';
    
    const beforeScreenshot = (page) => page.$('#root > *');
    
    initStoryshots({
      suite: 'Image storyshots',
      test: imageSnapshot({ storybookUrl: 'http://localhost:6006', beforeScreenshot }),
    });

    Install

    npm i @storybook/addon-storyshots-puppeteer

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    6.3.6

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    MIT

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