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.
See it in action!
When using cypress open
, errors are displayed in the GUI.
![Cypress Image Snapshot in action](https://user-images.githubusercontent.com/4060187/41942389-5a6705ae-796d-11e8-8003-fadbf7ccf43d.gif)
When an image diff fails, a composite image is constructed.
![Cypress Image Snapshot diff](https://user-images.githubusercontent.com/4060187/41942163-72c8c20a-796c-11e8-9149-c295341864d3.png)
When using cypress run
and --reporter cypress-image-snapshot/reporter
, diffs are output to your terminal.
![Cypress Image Snapshot reporter](https://user-images.githubusercontent.com/1153686/48518011-303d4580-e836-11e8-83ed-776acae78f9f.png)
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();
// 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);
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();
});
});
Run Cypress with --env updateSnapshots=true
in order to update the base image files for all of your tests.
Run Cypress with --env failOnSnapshotDiff=false
in order to prevent test failures when an image diff does not pass.
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 ๐.
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"
}
}
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
});
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:
- Take a screenshot with
cy.screenshot()
named according to the current test. - Check if a saved snapshot exists in
<rootDir>/cypress/snapshots
and if so diff against that snapshot. - If there is a resulting diff, save it to
<rootDir>/cypress/snapshots/__diff_output__
.
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
forcypress@>=3.0.0 <3.0.2
cypress-image-snapshot@>2.0.0
forcypress@>3.0.2
.