# Consumer-driven contract test

## Context

You have applied the \[\[Microservice architecture]] pattern. The application consists of numerous services. Services often invoke other services. You must write automated tests that verify that a service behaves correctly.

## Problem

How to easily test that a service provides an API that its clients expect?

## Solution

A test suite for a service that is written by the developers of another service that consumes it. The test suite verifies that the service meets the consuming service's expectations.

## Examples

[Spring Cloud Contract](https://cloud.spring.io/spring-cloud-contract/) is an open source project that supports this style of testing.

## Resulting context

This pattern has the following benefits:

* Testing a service in isolation is easier, faster, more reliable and cheap

This pattern has the following drawbacks:

* Tests might pass but the application will fail in production

This pattern has the following issues:

* How to ensure that the consumer provided tests match what the consumer actually requires?

## Related patterns

See \[\[Service Component Test]]

## See also

See \[\[Integration Contract Test]]