java-junit

Annotate the method with @ParameterizedTest instead of @Test and supply arguments via a source annotation. Use @ValueSource for single literals, @CsvSource for inline multi-parameter rows, @CsvFileSource for CSV files, @MethodSource for factory methods, and @EnumSource for enum constants.

Add @ExtendWith(MockitoExtension.class) to the test class, declare dependencies with @Mock, and inject them into the class under test with @InjectMocks. Stub behavior with when(...).thenReturn(...) so the unit test never touches real databases, clocks, or networks.

AssertJ's fluent assertThat(...) is preferred because it produces readable failure messages and rich type-specific checks. JUnit's built-in assertions like assertEquals and assertTrue remain available, and assertThrows or assertThatThrownBy both work for verifying exceptions.

Yes, spring-boot-starter-test bundles JUnit 5 including junit-jupiter-params, Mockito, and AssertJ, so no additional test dependencies are needed. Run the suite with ./mvnw test or ./gradlew test using the standard src/test/java layout.

Use plain JUnit 5 unit tests for isolated business logic with mocked collaborators. Switch to Spring Boot slice tests like @WebMvcTest or @DataJpaTest, or Testcontainers-based integration tests, when you need the Spring context, web layer, or a real database involved.