What is chromatic?
The npm package 'chromatic' is a tool designed to help developers automate visual testing for their UI components. It captures snapshots of components and runs visual regression tests to ensure that changes do not break the visual appearance of applications. Chromatic integrates with Storybook to manage component libraries and streamline the testing process.
What are chromatic's main functionalities?
Visual Testing
This code sample demonstrates how to add a visual test for a simple button component using Chromatic with Storybook. The 'withChromatic' decorator is used to enable Chromatic's snapshot capabilities for the component.
import { storiesOf } from '@storybook/react';
import { withChromatic } from 'chromatic/isolated';
storiesOf('Button', module)
.addDecorator(withChromatic)
.add('default', () => <button>Click me</button>);
Snapshot Management
This code configures Chromatic to take snapshots after a delay and at specified screen widths, facilitating responsive visual testing. It helps in managing how snapshots are captured based on different device widths.
import { configure } from '@storybook/react';
import { setChromaticOptions } from 'chromatic';
setChromaticOptions({
delay: 300, // Delay in ms before taking a snapshot
widths: [320, 1200] // Array of widths for responsive testing
});
configure(() => require('./stories'), module);
Other packages similar to chromatic
storybook
Storybook is a user interface development environment and playground for UI components. It facilitates building UI components in isolation and structuring a component library. While it does not offer visual regression testing by itself, it is often used in conjunction with Chromatic to provide that functionality.
percy
Percy by BrowserStack is a visual testing and review platform that integrates with your CI/CD pipeline. It captures screenshots of web pages and components, compares them against the baseline, and highlights visual changes. Percy offers a more comprehensive CI/CD integration compared to Chromatic, which is more tightly coupled with Storybook.
backstopjs
BackstopJS automates visual regression testing of web applications by comparing DOM screenshots over time. It is a standalone tool that can be used without Storybook, providing a different approach to visual testing compared to Chromatic's dependency on Storybook for component management.
Chromatic CLI
Publishes your Storybook to Chromatic and kicks off tests if they're enabled.
Documentation
š Read the Chromatic CLI docs
š View the Changelog
System requirements
The Chromatic CLI (and GitHub Action) is built to run in a variety of environments. We provide support for the following platforms:
- Latest (LTS) versions of Ubuntu, Windows (Server), macOS
- Node.js Current, Active or Maintenance (LTS) versions, according to their release schedule
- Storybook 6.5+
Other platforms/versions may work, but are not officially supported. Certain features may not be available on certain platforms/versions, even if otherwise supported.
Contributing
Contributions of any kind are welcome! We're available to chat via the Intercom widget on the documentation site.
Compatibility & versioning
Compatibility is guaranteed between this package and Chromatic like so:
- Production Chromatic ensures itās compatible with whatās on npm
- What's on the Git tag is equal to what's published on npm for that version
- This package ensures itās compatible with production Chromatic
To facilitate upgrading in the future, removing and adding features, this is the process:
- Any new features will have to be on Chromatic production before they could be used in this package
- We can add feature flags to be able to test new functionality
- Chromatic production can not remove any features this package depends on until after the usage has been removed from this package in addition to a grace period to allow users to upgrade
Building and running locally
- Ensure all dependencies are installed with
yarn install
- Build + watch the code locally:
yarn dev
- Run a build of all the CLI's stories against a Chromatic project:
yarn chromatic -t <token>
.
Running against staging
CHROMATIC_INDEX_URL=https://index.staging-chromatic.com yarn chromatic -t <token>
Running against development
To test against a local development version of the Chromatic stack, use
CHROMATIC_INDEX_URL=https://index.dev-chromatic.com yarn chromatic -t <token>
To only test a small number of test stories as a smoke test, use:
SMOKE_TEST=1 CHROMATIC_INDEX_URL=https://index.dev-chromatic.com yarn chromatic -t <token>
Publishing a new version
We use auto
to automate the release process. Versions are bumped, tags are created and the changelog is updated automatically. A new release goes out whenever a PR is merged to main
. A PR must have exactly one of the following labels before merging:
major
triggers a major version bumpminor
triggers a minor version bumppatch
triggers a patch version bump
Additionally, a PR may have exactly one of these labels:
release
creates a latest
release on npmskip-release
does not create a release at all (changes roll into the next release)
We have two types of releases:
latest
releases are the general audience production releases, used by most people. Automatically created when merging a PR with the release
label.canary
releases are intended for testing purposes and should not be used in production, as they may only work against a staging or dev environment. Automatically created on every PR, but does not auto-publish the GitHub Action.
For GitHub Actions, we may manually publish chromaui/action-canary
.
A script is provided to manually publish the GitHub Action, though it's typically only necessary for action-canary
releases:
yarn publish-action <canary|latest>