Pact Demo

A small demonstration of using Pact with Ruby and Docker.

Architecture

The demo contains 2 different services, a Consumer and a Provider. The code also assumes a Pact Broker as an external dependency.

Unit tests are intentionally not included to keep it simple and just show the tests needed for Pact to run.

Dependencies

Only two dependencies are required:

1. Docker
2. Docker Compose

Instructions

Within the consumer or provider directories, you can run:

	$ docker-compose run test

which will execute the Pact tests.

If you need to run rake tasks (eg. publishing a new version of a pact) you can run it with :

	$ docker-compose run test rake pact:publish

Pact overview

• Consumer Driven Contracts https://martinfowler.com/articles/consumerDrivenContracts.html

• A provider's CI build will fail if it does not meet consumer expectations

Pros

• More reliable service interactions

• Fast feedback integration testing

• No live testing environment required

Cons

• You can only use it when you control both ends (consumer and provider)

• It's a pain to setup, and a bit of a learning curve

• It's hard to understand (it's the inverse of how you usually think)

• It couples systems/services together and forces change a certain way (provider has to be changed first and requires backwards compatibility)

• Does not work well if consumer/provider is across team boundaries (consumers can break the provider's build)

Interesting Pact Things

Pact Broker Middle man for pacts Can also use local pact file Documentation Versioning

Rake Consumer -> Publish to Pact Broker Provider -> Verifies against pact

Pact Helper Consumer/Provider differences Configs

Integration spec Consumer Provider

Mock server

Logging Pact.log Mock server log

Changing contracts Changing Consumer first Changing Provider first