Unit testing services in Microservices - Architecture Diagram

System Overview - Unit testing services

This system focuses on unit testing individual microservices to ensure each service works correctly in isolation. Key requirements include fast feedback, test isolation, and mocking dependencies to avoid external calls.

Architecture Diagram

User
  |
  v
Test Runner
  |
  v
Mock Framework
  |
  v
Microservice Under Test
  |
  v
Mocked Dependencies

Components

User

actor

Developer or CI system triggering unit tests

Test Runner

service

Executes unit tests and reports results

Mock Framework

library

Simulates dependencies to isolate the microservice

Microservice Under Test

service

The microservice code being tested

Mocked Dependencies

service

Fake versions of external services or databases

Request Flow - 5 Hops

User → Test Runner

Test Runner → Mock Framework

Test Runner → Microservice Under Test

Microservice Under Test → Mocked Dependencies

Microservice Under Test → Test Runner

Failure Scenario

Component Fails:Mock Framework

Impact:Tests cannot isolate microservice; may call real dependencies causing slow or flaky tests

Mitigation:Use fallback mocks or skip tests until mock framework is fixed; isolate tests with containerization

Architecture Quiz - 3 Questions

Which component simulates external services during unit testing?

A Mock Framework

B Test Runner

C Microservice Under Test

D User

Design Principle

This architecture demonstrates the principle of isolating components during testing by using mocks to replace external dependencies. It ensures fast, reliable tests that focus on the microservice logic alone.