unit-tests

Use @ExtendWith(MockitoExtension.class) with @Mock for each constructor collaborator and @InjectMocks for the class under test. Constructor injection in src/main lets Mockito wire dependencies automatically, then stub with when(...).thenReturn(...) and verify interactions.

Use Mockito's MockedStatic inside a try-with-resources block within the test method, never as a class field. This prevents the static stub from leaking between tests and breaking parallel execution.

AssertJ is preferred for everything except the simplest assertEquals because it produces better failure messages and fluent chaining. Pick one library per repository and stay consistent; assertSoftly collects multiple failures in a single run.

Line coverage measures execution, not verification — tests can run code without asserting on results. PIT mutation testing seeds bugs into your code and reports which mutants survive, revealing tests that exercise code but never verify behavior.

Skip tests for classes with no logic such as pure DTOs, records, or Lombok @Getter holders. Instead, add them to the jacoco-maven-plugin excludes list so they do not distort coverage metrics.

Stub the HTTP boundary with MockWebServer or WireMock, enqueue mock responses with specific bodies and status codes, then assert deserialization and verify that non-2xx responses translate into domain exceptions.