cypress-image-snapshot
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    4.0.1 • Public • Published

    Cypress Image Snapshot

    Cypress Image Snapshot binds jest-image-snapshot's image diffing logic to Cypress.io commands. The goal is to catch visual regressions during integration tests.

    Discord

    See it in action!

    Cypress GUI

    When using cypress open, errors are displayed in the GUI.

    Cypress Image Snapshot in action

    Composite Image Diff

    When an image diff fails, a composite image is constructed.

    Cypress Image Snapshot diff

    Test Reporter

    When using cypress run and --reporter cypress-image-snapshot/reporter, diffs are output to your terminal.

    Cypress Image Snapshot reporter

    Installation

    Install from npm

    npm install --save-dev cypress-image-snapshot

    then add the following in your project's <rootDir>/cypress/plugins/index.js:

    const {
      addMatchImageSnapshotPlugin,
    } = require('cypress-image-snapshot/plugin');
    
    module.exports = (on, config) => {
      addMatchImageSnapshotPlugin(on, config);
    };

    and in <rootDir>/cypress/support/commands.js add:

    import { addMatchImageSnapshotCommand } from 'cypress-image-snapshot/command';
    
    addMatchImageSnapshotCommand();

    Syntax

    // addMatchImageSnapshotPlugin
    addMatchImageSnapshotPlugin(on, config);
    
    // addMatchImageSnapshotCommand
    addMatchImageSnapshotCommand();
    addMatchImageSnapshotCommand(commandName);
    addMatchImageSnapshotCommand(options);
    addMatchImageSnapshotCommand(commandName, options);
    
    // matchImageSnapshot
    .matchImageSnapshot();
    .matchImageSnapshot(name);
    .matchImageSnapshot(options);
    .matchImageSnapshot(name, options);
    
    // ---or---
    
    cy.matchImageSnapshot();
    cy.matchImageSnapshot(name);
    cy.matchImageSnapshot(options);
    cy.matchImageSnapshot(name, options);

    Usage

    In your tests

    describe('Login', () => {
      it('should be publicly accessible', () => {
        cy.visit('/login');
    
        // snapshot name will be the test title
        cy.matchImageSnapshot();
    
        // snapshot name will be the name passed in
        cy.matchImageSnapshot('login');
    
        // options object passed in
        cy.matchImageSnapshot(options);
    
        // match element snapshot
        cy.get('#login').matchImageSnapshot();
      });
    });

    Updating snapshots

    Run Cypress with --env updateSnapshots=true in order to update the base image files for all of your tests.

    Preventing failures

    Run Cypress with --env failOnSnapshotDiff=false in order to prevent test failures when an image diff does not pass.

    Reporter

    Run Cypress with --reporter cypress-image-snapshot/reporter in order to report snapshot diffs in your test results. This can be helpful to use with --env failOnSnapshotDiff=false in order to quickly view all failing snapshots and their diffs.

    If you using iTerm2, the reporter will output any image diffs right in your terminal 😎.

    Multiple reporters

    Similar use case to: https://github.com/cypress-io/cypress-example-docker-circle#spec--xml-reports

    If you want to report snapshot diffs as well as generate XML junit reports, you can use mocha-multi-reporters.

    npm install --save-dev mocha mocha-multi-reporters mocha-junit-reporter
    

    You'll then want to set up a cypress-reporters.json which may look a little like this:

    {
      "reporterEnabled": "spec, mocha-junit-reporter, cypress-image-snapshot/reporter",
      "mochaJunitReporterReporterOptions": {
        "mochaFile": "cypress/results/results-[hash].xml"
      }
    }

    where reporterEnabled is a comma-separated list of reporters.

    You can then run cypress like this:

    cypress run --reporter mocha-multi-reporters --reporter-options configFile=cypress-reporters.json

    or add the following to your cypress.json

    {
      ..., //other options
      "reporter": "mocha-multi-reporters",
      "reporterOptions": {
        "configFile": "cypress-reporters.json"
      }
    }
    

    Options

    • customSnapshotsDir : Path to the directory that snapshot images will be written to, defaults to <rootDir>/cypress/snapshots.
    • customDiffDir: Path to the directory that diff images will be written to, defaults to a sibling __diff_output__ directory alongside each snapshot.

    Additionally, any options for cy.screenshot() and jest-image-snapshot can be passed in the options argument to addMatchImageSnapshotCommand and cy.matchImageSnapshot(). The local options in cy.matchImageSnapshot() will overwrite the default options set in addMatchImageSnapshot.

    For example, the default options we use in <rootDir>/cypress/support/commands.js are:

    addMatchImageSnapshotCommand({
      failureThreshold: 0.03, // threshold for entire image
      failureThresholdType: 'percent', // percent of image or number of pixels
      customDiffConfig: { threshold: 0.1 }, // threshold for each pixel
      capture: 'viewport', // capture viewport in screenshot
    });

    How it works

    We really enjoy the diffing workflow of jest-image-snapshot and wanted to have a similar workflow when using Cypress. Because of this, under the hood we use some of jest-image-snapshot's internals and simply bind them to Cypress's commands and plugins APIs.

    The workflow of cy.matchImageSnapshot() when running Cypress is:

    1. Take a screenshot with cy.screenshot() named according to the current test.
    2. Check if a saved snapshot exists in <rootDir>/cypress/snapshots and if so diff against that snapshot.
    3. If there is a resulting diff, save it to <rootDir>/cypress/snapshots/__diff_output__.

    Cypress Version Requirements

    Cypress's screenshot functionality has changed significantly across 3.x.x versions. In order to avoid buggy behavior, please use the following version ranges:

    • cypress-image-snapshot@>=1.0.0 <2.0.0 for cypress@>=3.0.0 <3.0.2
    • cypress-image-snapshot@>2.0.0 for cypress@>3.0.2.

    Keywords

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    Install

    npm i cypress-image-snapshot

    DownloadsWeekly Downloads

    217,151

    Version

    4.0.1

    License

    MIT

    Unpacked Size

    21.9 kB

    Total Files

    8

    Last publish

    Collaborators

    • jaredpalmer
    • jayjaycross
    • cypress-image-snapshot