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How not to break everything

When we made first made the change to the pact on the master branch of the consumer, we ended up with broken consumer and provider builds, stopping them both from releasing. In the previous step, we learned how to configure the provider so that it could still continue to be released, even if it was not able to successfully verify the new pact.

The consumer is still unable to make a release from its master however, as the can-i-deploy step correctly identifies that the verification for the master pact has failed. This is a correct report on the state of this integration - the API does not yet implement the features we require to deploy.

Let's make our changes on a branch this time.

  1. In the consumer codebase, revert the change to master and push to make the build go green again.

    git revert HEAD
    git push

  2. Create a new branch

      git checkout -b feat/new-field

  3. open up src/api.pact.spec.js, scroll down to the first test, and in the expectedProduct definition, add a new field e.g. color: "red".

  4. Make sure the tests pass locally by running make test.

  5. Commit & Push your changes by running

    1. git add src/api.pact.spec.js
    2. git commit -m 'feat: add color'
    3. git push --set-upstream origin feat/new-field.
    • The consumer tests will pass, and then the CI build will fail as can-i-deploy correctly identifies that this branch is not yet compatible with the API (there is no verifications against this changed pact content, and therefore the provider must verify it).
      • Our pact associated with the feature branch feat/new-field will be unverified and the consumer cannot deploy this feature branch until the provider implements the feature.
    • The webhook-triggered pact verification provider build will be triggered
      • It will verify the changed pact against the latest providers main branch and any deployed (or released) in production
      • It will fail, that's ok, as it wouldn't stop the provider from deploying as we have enabled the pendingPacts feature
      • Our pact associated with the feature branch feat/new-field will be verified as incompatible and the consumer cannot deploy.
      • If we re-run our can-i-deploy step of the failed consumer build, we will see it will now show a failed verification.

👉 The can-i-deploy step acts as a "can I merge?" check when run from a branch. We'll know we're safe to merge this branch into master if/when can-i-deploy passes. 👈

Expected state by the end of this step​

  • In Github Actions:
    • A master consumer build that passes and deploys.
    • A feat/new-field consumer build that fails at can-i-deploy.
  • In PactFlow:
    • A master pact with a successful verification result.
    • A feat/new-field pact with a failed verification result

Conclusion​

By making changes on a branch of the consumer, and publishing a 'feature pact', we keep our main release branch green, and make sure we're not blocked from deploying. The can-i-deploy call acts as a "can I merge?" check when we're on a branch.