Visual Regression Testing for Storybook

Rationale

There are a few visual regression tools for the web, but most either cannot be run headless or use phantomjs which is deprecated and a browser nobody is actually using. They usually also require you to maintain fixtures. With react-native it's now possible to target multiple platforms with a single code base, but there's no single tool to test all to my knowledge.

Loki aims to have easy setup, no to low maintenance cost, reproducible tests independent of which OS they are run on, runnable on CI and support all platforms storybook does.

Supported platforms

• Chrome in docker (recommended)
• Chrome in AWS Lambda
• Local Chrome application
• iOS simulator
• Android emulator

Prerequisites

• Node 16+

Optional dependencies

• GraphicsMagick for gm diffing engine, brew install graphicsmagick
• Docker for the chrome.docker target.
• Chrome 59+ for the chrome.app target, brew cask install google-chrome-canary.

Installation

yarn add loki --dev
yarn loki init

Workflow

Loki will not start any servers for you, so ensure storybook and any simulator/emulator is up and running before running tests.

1. Start storybook server yarn storybook
2. Add first set of reference files yarn loki update
3. Do some changes to your components
4. Test against references yarn loki test
5. Review changes in diff folder
6. Approve changes and update references yarn loki approve

Documentation

• Introduction
• Getting started
• Configuration
• Command line arguments

Examples

• React example
• React Native example

Development

# Install dependencies
yarn
# Start example storybook
yarn workspace @loki/example-react run storybook
# Run example visual tests
yarn workspace @loki/example-react run test
# Run unit tests
yarn test
# Run cli integration tests
cd test/cli && yarn test

Maintainers

License

MIT License. © Joel Arvidsson 2017-present