unit-test-service-layer

Unit test service layer logic by mocking dependencies with Mockito and JUnit 5. Use @ExtendWith(MockitoExtension.class), @Mock for dependencies, and @InjectMocks for the service under test. This isolates business logic and runs tests quickly without database or API calls.

Yes, use Mockito to mock repository and client dependencies, then verify their interactions and assert service outcomes. This lets you test service orchestration and edge cases without actual database or API calls.

Use Mockito's verification methods to confirm repositories and clients are called with expected arguments and return values. Combine interaction verification with AssertJ assertions to validate both collaborator behavior and service outcomes.

No. Mock all external dependencies with Mockito so tests run in isolation without a database, Spring container, or API calls. This provides fast feedback and deterministic test results.

Mock each dependency separately, then orchestrate them in your test to simulate multi-service workflows. Use @Mock for each collaborator, @InjectMocks for the service, and Mockito's when() and verify() to control and assert interactions.

Add Mockito and JUnit 5 to your build dependencies. Mockito provides mocking and interaction verification; JUnit 5 provides the test framework and @ExtendWith(MockitoExtension.class) integrates them for service layer unit testing.