Unit testing services in Microservices - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why isolate dependencies in unit testing microservices?

In unit testing a microservice, why is it important to isolate its dependencies?

A To deploy the microservice faster in production

B To speed up the entire system by running all services simultaneously

C To test the network latency between microservices

D To ensure tests only verify the microservice's own logic without interference from other services

💡 Hint

Think about what unit testing aims to verify.

Unit testing focuses on the internal logic of a single component. Isolating dependencies prevents external factors from affecting test results.

❓ Architecture

intermediate

Best practice for mocking external service calls in microservice unit tests

Which approach is best for mocking external service calls when unit testing a microservice?

A Use a mocking framework to replace external service calls with predefined responses

B Use a database snapshot to simulate external service data

C Skip testing external calls and only test internal methods

D Call the real external services to verify integration

💡 Hint

Consider how to keep unit tests fast and reliable.

Mocking frameworks allow replacing external calls with controlled responses, keeping tests fast and focused.

❓ scaling

advanced

Scaling unit tests for a microservice with many dependencies

You have a microservice with many external dependencies. How can you scale unit testing effectively?

A Test only the main dependency and ignore others

B Run integration tests only and skip unit tests

C Create mocks for all dependencies and use test doubles to simulate their behavior

D Manually test the microservice in production environment

💡 Hint

Think about how to keep unit tests manageable and reliable.

Using mocks and test doubles for all dependencies allows unit tests to remain fast and focused despite many dependencies.

❓ tradeoff

advanced

Tradeoff of using real databases vs mocks in microservice unit tests

What is a key tradeoff when choosing between using a real database or mocks in microservice unit tests?

A Mocks always cause tests to fail; real databases never fail

B Real databases provide realistic tests but slow down test execution; mocks are faster but less realistic

C Using real databases eliminates the need for unit tests

D Mocks require more hardware resources than real databases

💡 Hint

Consider speed versus realism in tests.

Real databases test actual data interactions but slow tests; mocks speed tests but may miss real issues.

❓ estimation

expert

Estimating test coverage impact of unit tests on a microservice with 10 endpoints

A microservice has 10 endpoints. Each endpoint has 5 main logic branches. If unit tests cover 80% of all branches, how many branches are tested?

A 40

B 50

C 80

D 100

💡 Hint

Calculate total branches and then apply coverage percentage.

Total branches = 10 endpoints * 5 branches = 50. 80% of 50 = 40 branches tested.