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# Service Component 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 do you easily test a service?

## Forces

* End to end testing (i.e. tests that launch multiple services) is difficult, slow, brittle, and expensive.

## Solution

A test suite that tests a service in isolation using test doubles for any services that it invokes.

## 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 test doubles always correctly emulate the behavior of the invoked services?

## Related patterns

See \[\[Service Integration Contract Test]]

## See also

See \[\[Component Testing]]