Prerequisite concepts

Tags are simple String values that that belong to "pacticipant" version (that is, application version) resources in the Pact Broker. They are used to provide metadata about a version - the most common use case being to indicate the git branch of a version (eg. master).

Tags are used to make sure we are verifying the right pacts.

In the Makefile file in the consumer project, we tag the consumer version with the name of the branch when we publish the pacts.

publish_pacts:
  @"${PACT_CLI}" publish ${PWD}/pacts --consumer-app-version ${GIT_COMMIT} --tag ${GIT_BRANCH}

In the src/product/product.pact.test.js file in the provider project, we have configured the verification task to fetch the pacts that belong to the latest consumer versions with the master tag ({ tag: 'master', latest: true }), and the pacts that belong to the currently deployed versions ({ deployed: true } - we'll explain how the broker knows which versions are deployed in the next section).

const fetchPactsDynamicallyOpts = {
  ...,
  provider: "pactflow-example-provider",
  consumerVersionSelectors: [{ tag: 'master', latest: true }, { deployed: true }],
  ...
}

When we publish the verifications, we similarly tag the provider version with the git branch.

const baseOpts = {
  ...,
  providerVersion: process.env.GIT_COMMIT,
  providerVersionTags: [process.env.GIT_BRANCH],
  ...
}

To allow Pact to ensure your APIs are always backwards compatible with the consumer versions that are in production, the Pact Broker needs to know which application versions are actually in production. To do this, we use the record-deployment command that comes with the Pact Broker CLI. You will see this in the Makefile of each project.

record_deployment:
    @"${PACT_CLI}" broker record-deployment --pacticipant ${PACTICIPANT} --version ${GIT_COMMIT} --environment production

Though our example is hardcoded to "production", this command should be run after a successful deployment to any environment for both consumers and providers. The "production" and "test" environments have been seeded for you in your API Hub for Contract Testing account, but if you want to add any more environments, you will need to add them yourself using the Pact Broker CLI.

For mobile applications and code libraries that are "released" to an app store/repository rather than being "deployed", the "record-release" command should be used. It's not relevant for this workshop, but you can read more about it here if/when you need to.

Recording the deployment allows us to use the consumer version selector { deployed: true } in src/product/product.pact.test.js, to make sure we are verifying the pacts for all the currently deployed versions.

It also allows us to use the can-i-deploy command (more on this later) to make sure we're safe to deploy to an environment.