Contract testing POC using Pact framework

• Contract testing is done from the consumer and provider perspective with a pact broker between them.
• Pact broker is turned on by docker-compose up and running on localhost:9292
• Consumer is creating the contract (by pact dsl or wiremock + conversion to pact) -> run unit tests against stubs -> publish to pact broker is done by a gradle plugin
• Provider is pulling pact files from broker by starting tests -> set the necessary states -> run tests against it's system (just a mock in this case) -> publish verification result to pact broker

Thoughts and conclusions

• Viable E2E testing replacement
• Incredible practical potential
• Unpolished syntax
• Difficult to configure
• Consumer creating expectations from Provider, expressing them in a pact file, Provider checking expectations on Consumer behalf

Consumer side

• Should be done by developers (run simple 'integration' unit tests against pact stubs, thus resulting in functionality checking the contract against your microservice)
• Use pact dsl consumer instead of wiremock + conversion to pact, it will always give you more functionality
• It's not replacement for wiremock, as all pact test must use @State by Provider, thus limiting possible scenarios
• Write dedicated tests for contract testing covering the essential functionality using provided @State of Provider

Provider side

• Should be done by testers (pact will test Consumer's expectations described by the pact file against a real environment, provide @State that can be accomplished in that environment for Consumer pacts)
• Pact is doing most of the job, you just need to provide him a http client to check the pacts (run the pact tests) and provide states (@State) for the consumers to use

Built using

• Kotlin
• Micronaut
• Pact
• Junit5
• Docker