testing-junit

Reliable Java unit tests use JUnit 5 annotations, Mockito mocks, and AssertJ assertions to verify application logic, catch regressions early, and ensure correct behavior. Structured test organization includes nested tests and parameterized scenarios.

Spring Boot controller testing uses MockMvc with @WebMvcTest to verify web layer behavior. This approach applies JUnit 5 and AssertJ to validate HTTP request handling and response mapping without deploying the full application context.

Testcontainers enables real database interactions during integration tests. Combined with JUnit 5, it provisions containerized databases, ensuring tests validate actual database behavior and detect regressions in data access logic.

Parameterized and nested tests in JUnit 5 structure complex test scenarios by grouping related cases and running them across multiple inputs. AssertJ soft assertions verify multiple conditions within these structured tests without stopping on the first failure.

Using AssertJ with Mockito mocks provides fluent assertions that improve test readability. While Mockito handles mock interactions, AssertJ verifies complex object states and soft assertions, ensuring robust test coverage for Java application logic.

JUnit 5 and AssertJ improve regression detection through parameterized tests, nested test organization, and fluent assertions. This combination provides structured test coverage for unit tests, integration tests, and Spring Boot contexts.