Consumer Driven Contract Tests

A simple demonstration of how to implement consumer driven contract tests using the pact-jvm framework.

This project aims to mimic a contract between an Android weather app and a weather API. We will be building the bare minimum of components for this to work. This includes an HTTP Client to call our API, as well as a tiny Micronaut app to serve hard-coded responses. We will be using the Kotlin Fuel library to make http requests to the API. This application is not feature complete, and only serves to demonstrate consumer contracts between two applications.

This repository contains two modules, one for the consumer and another for the provider.

The API that we will develop should be an HTTP GET endpoint, taking a query parameter id which is the cityId of the location of interest. The API should then respond with the following JSON response body:

{
  "clouds": {
    "all": 2
  },
  "id": 1851632,
  "main": {
    "humidity": 92,
    "pressure": 1009,
    "temp": 289.92,
    "temp_max": 290.93,
    "temp_min": 288.71
  },
  "name": "Shuzenji",
  "timezone": 32400,
  "weather": {
    "description": "clear sky",
    "main": "Clear"
  },
  "wind": {
    "deg": 107.538,
    "speed": 0.47
  }
}

The main branch of this repository contains an unimplemented application that can be developed using the following pointers:

The solution branch contains a working implementation for reference.

Consumer in Kotlin

1. Add build dependencies to the consumer Gradle build file:

implementation("com.github.kittinunf.fuel:fuel:2.2.1")
implementation("com.github.kittinunf.fuel:fuel-gson:2.2.1")
testImplementation("au.com.dius:pact-jvm-consumer-junit_2.11:3.5.0")

2. Create a new Kotlin test class ConsumerPact
3. Extend the au.com.dius.pact.consumer.ConsumerPactTestMk2
4. Implement the overrides for the providerName and consumerName methods.
5. Implement the createPact method, observing the above contract.
6. Write a WeatherClient class to call a remote weather API. This class should be constructed with url and appid fields, and should expose a method with the following signature: getWeatherByCoords(lat: Double, lon: Double). Use Fuel to make a blocking call to the API endpoint.
7. Implement the runTest method, using the WeatherClient to call the injected mockServer. Assert the response and confirm that it is working.

Provider in Java with Micronaut

1. Apply the id "au.com.dius.pact" version "4.0.0" to the provider Gradle build.
2. Add the following dependencies for the Micronaut framework:

annotationProcessor platform("io.micronaut:micronaut-bom:$micronautVersion")
annotationProcessor "io.micronaut:micronaut-inject-java"
annotationProcessor "io.micronaut:micronaut-validation"
implementation platform("io.micronaut:micronaut-bom:$micronautVersion")
implementation "io.micronaut:micronaut-inject"
implementation "io.micronaut:micronaut-validation"
implementation "io.micronaut:micronaut-runtime"
implementation "javax.annotation:javax.annotation-api"
implementation "io.micronaut:micronaut-http-server-netty"
implementation "io.micronaut:micronaut-http-client"
runtimeOnly "ch.qos.logback:logback-classic:1.2.3"

3. The micronautVersion can be set to the current stable version in the settings.gradle.kts
4. Write a provider configuration to point to localhost:8080 and reference the pact contract file.
5. Implement startProviderTask and terminateProviderTask hooks to start/stop the running server.
6. Write an Application bootstrap class.
7. Write a WeatherController class to serve back the above JSON response for given longitude, latitude and appid parameters.

Running from the command line

$ ./gradlew :consumer:test
$ cat consumer/target/pacts/weather-consumer-weather-provider.json
$ ./gradlew :provider:run

Open a new terminal in the project directory and:

$ ./gradlew :provider:pactVerify