Lost Pixel visual regression testing #

Lost Pixel is a modern open-source visual regression testing tool that allows you to run self-hosted visual regression tests. Lost Pixel Platofrm is for teams and is a cloud version of visual testing.

Setting up self-hosted visual testing #

Lost Pixel has first-class Histoire support meaning that you don't need to do much to add visual tests to your app if you have your Histoire book ready!

Start with installing lost-pixel by npm install lost-pixel and creating a lostpixel.config.js|ts file with following contents.

import { CustomProjectConfig } from 'lost-pixel';

export const config: CustomProjectConfig = {
  histoireShots: {
    histoireUrl: './.histoire/dist',
  },
  generateOnly: true,
  failOnDifference: true
};

Before running visual tests you need to have your Histoire book built first.

This setup allows you to run visual tests locally. To test your stories run npx lost-pixel

To update the baselines run npx lost-pixel update.

GitHub actions #

To run your tests on CI you can use lost-pixel action utility. If you are running on any other CI provider - lost-pixel is a docker image that is runnable on CI of your choice(only within GitHub currently though)

on: [push]

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout
        uses: actions/checkout@v3

      - name: Setup Node
        uses: actions/setup-node@v3
        with:
          node-version: 18.x
          cache: 'npm'

      - name: Install dependencies
        run: npm install

      - name: Build histoire
        run: npm run story:build

      - name: Lost Pixel
        uses: lost-pixel/lost-pixel@v3.8.0

To update baselines locally run npx lost-pixel docker update, this will ensure that lost-pixel runs in docker and there are no OS differences in rendering between CI and local tests.

Lost Pixel Platform #

If you have self-hosted version of tests working it is not complicated to migrate to Lost Pixel Platform. Follow this guide to achieve that.