Automate Chromatic with Travis CI

Chromatic’s automation can be included as part of your Travis CI job with relative ease.

Setup

To integrate Chromatic with your existing workflow, you’ll need to add the following:

# travis.yml

# Other required configuration

jobs:
  include:
     # Other jobs

     # 👇 Adds Chromatic as a job
   - name: 'Publish to Chromatic'
     script: yarn chromatic --project-token=${CHROMATIC_PROJECT_TOKEN}
For extra security, add Chromatic's project-token as an environment variable. See the official Travis CI environment variables documentation.

Run Chromatic on specific branches

If you need to customize your workflow to run on specific branches, you can do so. Change your travis.yml to the following:

# travis.yml

# Other required configuration

branches:
  only: main # 👈 Filters the execution to run only on the main branch

jobs:
  include:
     # Other jobs

     # 👇 Adds Chromatic as a job
   - name: 'Publish to Chromatic'
     script: yarn chromatic --project-token=${CHROMATIC_PROJECT_TOKEN}
Read the official Travis CI conditional build documentation.

Travis CI like other CI systems offer the option of running builds for various types of events. For instance for commits pushed to a branch in a pull request. Or for “merge” commits between that branch and the base branch (main).

These specific types of commits (merge) don’t persist in the history of your repository. That can cause Chromatic’s baselines to be lost in certain situations.

For internal pull requests (ie. pull requests that aren’t from forks) we recommend disabling Chromatic on pr build events. Also make sure you have push builds enabled in your settings.

Once these conditions are met, add the following code to your .travis.yml:

# travis.yml

# Other required configuration

jobs:
  include:
     # Other jobs

     # 👇 Adds Chromatic as a job
   - name: 'Publish to Chromatic'
     # 👇 Verifies the build event type or a if it's a forked repository
     if: (type = push OR head_repo != repo )
     script: yarn chromatic --project-token=${CHROMATIC_PROJECT_TOKEN}

For external pull requests (i.e forked repositories), the above code will ensure Chromatic runs with the pr build event, because Travis will not trigger push events for these cases.

UI Test and UI Review

UI Tests and UI Review rely on branch and baseline detection to keep track of snapshots. We recommend the following configuration.

Command exit code for “required” checks

If you are using pull request statuses as required checks before merging, you may not want your Travis build to fail if test snapshots render without errors (but with changes). To achieve this, pass the flag --exit-zero-on-changes to the chromatic command, and your job will continue in such cases. For example:

# travis.yml

# Other required configuration

jobs:
  include:
     # Other jobs

     # 👇 Adds Chromatic as a job
   - name: 'Publish to Chromatic'
     # 👇 Runs Chromatic with the flag to prevent workflow failure
     script: yarn chromatic --project-token=${CHROMATIC_PROJECT_TOKEN} --exit-zero-on-changes

When using --exit-zero-on-changes your build will still stop and fail if your Storybook contains stories that error. If you’d prefer Chromatic never to block the build, you can use yarn chromatic || true.

Re-run failed builds after verifying UI test results

Builds that contain visual changes need to be verified. They will fail if you are not using --exit-zero-on-changes. Once you accept all the changes, re-run the build and the Publish to Chromatic job will pass.

If you deny any change, you will need to make the necessary code changes to fix the test (and thus start a new build) to get Chromatic to pass again.

Maintain a clean “main” branch

A clean main branch is a development best practice and highly recommended for Chromatic. In practice, this means ensuring that test builds in your main branch are passing.

If the builds are a result of direct commits to main, you will need to accept changes to keep the main branch clean. If they’re merged from feature-branches, you will need to make sure those branches are passing before you merge into main.

Squash/rebase merge and the “main” branch

We use GitHub, GitLab, and Bitbucket APIs respectively to detect squashing and rebasing so your baselines match your expectations no matter your Git workflow (see Branching and Baselines for more details).

If you’re using this functionality but notice the incoming changes were not accepted as baselines in Chromatic, then you’ll need to adjust the workflow and include a new Chromatic job with the --auto-accept-changes flag. For example:

# travis.yml

# Other configuration here

jobs:
  include:
     # 👇 Checks if the branch is not main and runs Chromatic
   - name: 'Publish to Chromatic'
     if: branch != main 
     script: yarn chromatic --project-token=${CHROMATIC_PROJECT_TOKEN}
     # 👇 Checks if the branch is main and runs Chromatic with the flag to accept all changes
   - name: 'Publish to Chromatic and auto accepts changes'
     if: branch = main
     script: yarn chromatic --project-token=${CHROMATIC_PROJECT_TOKEN} --auto-accept-changes

Including the --auto-accept-changes flag ensures all incoming changes will be accepted as baselines. Additionally, you’ll maintain a clean main branch.

If you want to test the changes introduced by the rebased branch, you can adjust your workflow and include a new step with the ignore-last-build-on-branch flag. For example:

# travis.yml

# Other required configuration

jobs:
  include:
     # Other jobs

     # 👇 Adds Chromatic as a job
   - name: 'Publish to Chromatic'
     # 👇 Option to skip the last build on target branch
     script: yarn chromatic --project-token=${CHROMATIC_PROJECT_TOKEN} --ignore-last-build-on-branch=my-branch

Including the --ignore-last-build-on-branch flag ensures the latest build for the specific branch is not used as a baseline.

Run Chromatic on external forks of open source projects

You can enable PR checks for external forks by sharing your project-token where you configured the Chromatic command (often in package.json or in the job).

There are tradeoffs. Sharing project-token‘s allows contributors and others to run Chromatic. They’ll be able to use your snapshots. They will not be able to get access to your account, settings, or accept baselines. This can be an acceptable tradeoff for open source projects who value community contributions.

Skipping builds for certain branches

Sometimes you might want to skip running a build for a certain branch, but still have Chromatic mark the latest commit on that branch as “passed”. Otherwise pull requests could be blocked due to required checks that remain pending. To avoid this issue, you can run chromatic with the --skip flag. This flag accepts a branch name or glob pattern.

One use case for this feature is skipping builds for branches created by a bot. For instance, Dependabot automatically updates a projects dependencies. Although some dependencies can result in UI changes, you might not find it worthwhile to run Chromatic for every single dependency update. Instead, you could rely on Chromatic running against the main or develop branch.

To skip builds for dependabot branches, use the following:

chromatic --skip 'dependabot/**'

To apply this to multiple branches, use an “extended glob”. See picomatch for details.

chromatic --skip '@(renovate/**|dependabot/**)'