Recommended configuration for verifying pacts

There are typically two different reasons why a pact verification task will need to be run.

1. When the provider makes a change
   • In this situation, a full "regression suite" pact verification needs to be made for all the consumers and all the supported stages (eg. test, production) to ensure that backwards compatibility is maintained.
2. When a pact changes
   • In this situation, only the changed pact needs to be verified.

Verification triggered by provider change

The following examples require support for the "pacts for verification" API in your Pact library which you can read about here.

Consumer Version Selectors

If using branches/environments

See this blog post on branches and environments.

• The minimum pact that should be verified is the latest pact from the main line of development from the consumer (eg. { "mainBranch": true }). This requires that the consumer has configured the branch when publishing the pact.
• If you have matured your Pact workflow to the stage that you are recording deployments in the Pact Broker when you deploy to an environment, then you should include selectors for the deployed and released versions (eg. { "deployedOrReleased": true } )
• A common pattern to use when adding new features is for the provider to make a branch with the same name as the consumer's branch (which is used to create the consumer version tag), and to use a selector to find the matching branch (eg. { "matchingBranch": true }). This way, the provider Pact configuration doesn't need to be modified to pull in the matching pact.
  • The pacts will be de-duplicated, so if the GIT_BRANCH is main, you'll still only get one pact to verify. If there are no pacts for the current GIT_BRANCH, the selector will just be ignored.
  • If you can't dynamically determine the tags of the feature pacts you want to verify, you will have to change the selectors while you are on a branch, and then put them back to normal once you've merged.

If using tags

This not recommended if you are on versions of the Pact Broker and Pact libraries that support branches and environments.

• The minimum pact that should be verified is the latest pact from the main line of development from the consumer (eg. { tag: "main", latest: true }). This requires that the consumer has configured their tag to be the name of the git branch when publishing the pact.

• If you have matured your Pact workflow to the stage that you are tagging your application versions in the Pact Broker when you deploy to an environment, then you should include selectors for your various environments (eg. test, production).

• A common pattern to use when adding new features is for the provider to make a branch with the same name as the consumer's branch (which is used to create the consumer version tag), and to configure a selector that uses the name of the current provider branch (eg. { tag: process.env.GIT_BRANCH, latest: true }). This way, the provider Pact configuration doesn't need to be modified to pull in the matching pact.

  • The pacts will be de-duplicated, so if the GIT_BRANCH is main, you'll still only get one pact to verify. If there are no pacts for the GIT_BRANCH tag, the selector will just be ignored.

  • If you can't dynamically determine the tags of the feature pacts you want to verify, you will have to change the selectors while you are on a branch, and then put them back to normal once you've merged.

Pending pacts

Enabling the pending pacts feature stops changed pacts breaking the main provider build. If you are automatically bringing in a pact using the "matching feature branch names" approach, you might want to disable this feature on your feature branches, so that a feature pact correctly fails the branch build until it is fully implemented, and then passes to let you know you can merge.

Work in progress pacts

Including work in progress pacts allows newly changed pacts to be verified without having to manually change the configuration. You may wish to only enable this feature on your main line of development, as if you are on a branch, you are probably either trying to fulfill a specific pact, or you aren't changing any Pact related code at all.

Examples

Javascript

Using branches and environments

const verificationOptions = {
  // ....
  provider: "example-provider",
  pactBrokerUrl: "http://test.pactflow.io",
  consumerVersionSelectors: [
    {
      mainBranch: true
    },
    {
      matchingBranch: true
    },
    {
      deployedOrReleased: true
    }
  ],
  enablePending: true,
  ...(process.env.GIT_BRANCH === "main"
? {
    includeWipPactsSince: "2020-01-01",
  }
: {})

  // used when publishing verification results
  publishVerificationResult: process.env.CI === "true", //only publish from CI
  providerVersion: process.env.GIT_COMMIT, //use the appropriate env var from your CI system
  providerVersionBranch: process.env.GIT_BRANCH,  //use the appropriate env var from your CI system
}

Using tags (this approach is now superseded by branches and environments)

const verificationOptions = {
  // ....
  provider: "example-provider",
  pactBrokerUrl: "http://test.pactflow.io",
  consumerVersionSelectors: [
    {
      tag: "main",
      latest: true
    },
    {
      tag: process.env.GIT_BRANCH,
      latest: true
    },
    {
      tag: "test",
      latest: true
    },
    {
      tag: "production",
      latest: true
    }
  ],
  enablePending: true,
  includeWipPactsSince: process.env.GIT_BRANCH === "main" ? "2020-01-01" : undefined,

  // used when publishing verification results
  publishVerificationResult: process.env.CI === "true", //only publish from CI
  providerVersion: process.env.GIT_COMMIT, //use the appropriate env var from your CI system
  providerVersionTags: process.env.GIT_BRANCH ? [process.env.GIT_BRANCH] : [],
}

Ruby

Using branches and environments

  # The git commands are just for local testing, not needed for real CI
  provider_version = ENV['GIT_COMMIT'] || `git rev-parse --verify HEAD`.strip
  provider_branch = ENV['GIT_BRANCH'] || `git name-rev --name-only HEAD`.strip
  publish_results = ENV['CI'] == 'true' # results should only be published from CI
  # choose the appropriate credentials for your broker
  credentials = {
    username: ENV['PACT_BROKER_USERNAME'],
    password: ENV['PACT_BROKER_PASSWORD'],
    token: ENV['PACT_BROKER_TOKEN']
  }.compact

  Pact.service_provider "example-provider" do
    app_version provider_version
    app_version_branch provider_branch
    publish_verification_results publish_results
    
    honours_pacts_from_pact_broker do
      pact_broker_base_url 'http://test.pactflow.io', credentials

      consumer_version_selectors [
          { main_branch: true },
          { matching_branch: true },
          { deployed_or_released: true }
      ]
      enable_pending true
      include_wip_pacts_since provider_branch == "main" ? "2020-01-01" : nil
    end
  end

Using tags (this approach is now superseded by branches and environments)

  # The git commands are just for local testing, not needed for real CI
  provider_version = ENV['GIT_COMMIT'] || `git rev-parse --verify HEAD`.strip
  provider_branch = ENV['GIT_BRANCH'] || `git name-rev --name-only HEAD`.strip
  publish_results = ENV['CI'] == 'true' # results should only be published from CI
  # choose the appropriate credentials for your broker
  credentials = {
    username: ENV['PACT_BROKER_USERNAME'],
    password: ENV['PACT_BROKER_PASSWORD'],
    token: ENV['PACT_BROKER_TOKEN']
  }

  Pact.service_provider "example-provider" do
    app_version provider_version
    app_version_tags [provider_branch]
    publish_verification_results publish_results
    
    honours_pacts_from_pact_broker do
      pact_broker_base_url 'http://test.pactflow.io', credentials

      consumer_version_selectors [
          { tag: 'main', latest: true },
          { tag: provider_branch, latest: true },
          { tag: 'test', latest: true },
          { tag: 'production', latest: true }
      ]
      enable_pending true
      include_wip_pacts_since provider_branch == "main" ? "2020-01-01" : nil
    end
  end

Verification triggered by a contract requiring verification published

When a pact has changed, a webhook in the Pact Broker will kick off a build of the provider, passing through the URL of the pact that has changed. See this section of the CI/CD set up guide for more information on this.

Using this webhook event allows the changed pact to be tested against the head of the providers main branch and any deployed or released versions of the provider, in the same way as the consumer version selectors can be configured to allow the head of the consumers main branch and any deployed or released versions of the pact to be tested against a version of the provider.

More details on the webhook can be found in the webhook documentation

When the pact URL is known, the pactBrokerUrl, providerName, consumerVersionSelectors/consumerVersionTags, enablePending, includeWipPactsSince fields should not be set. You can see an example of switching between the two verification modes (all vs changed) in this Node example

Examples

You can find samples in our webhook template library for common build systems and see below for how to configure your provider build to use the pact URL.

Javascript

const verificationOptions = {
  pactUrls: [process.env.PACT_URL],

  // used when publishing verification results

  publishVerificationResult: process.env.CI === "true", //only publish from CI
  providerVersion: process.env.GIT_COMMIT, //use the appropriate env var from your CI system
  providerVersionBranch: process.env.GIT_BRANCH // if using branches and environments (recommended)
  providerVersionTags: process.env.GIT_BRANCH ? [process.env.GIT_BRANCH] : [], // optional, it is recommend you set the branch as well.
}

Ruby

PACT_BROKER_BASE_URL="..." # also set PACT_BROKER_USERNAME/PACT_BROKER_PASSWORD or PACT_BROKER_TOKEN
bundle exec rake pact:verify:at[${PACT_URL}]