Test-driven development for Quarkus 3.x LTS using JUnit 5, Mockito, REST Assured, Camel testing, and JaCoCo. Use when adding features, fixing bugs, or refactoring event-driven services.

Quarkus TDD Workflow TDD guidance for Quarkus 3.x services with 80%+ coverage (unit + integration). Optimized for event driven architectures with Apache Camel. When to Use New features or REST endpoints Bug fixes or refactors Adding data access logic, security rules, or reactive streams Testing Apache Camel routes and event handlers Testing event driven services with RabbitMQ Testing conditional flow logic Validating CompletableFuture async operations Testing LogContext propagation Workflow 1. Write tests first (they should fail) 2. Implement minimal code to pass 3. Refactor with tests green 4. Enforce coverage with JaCoCo (80%+ target) Unit Tests with @Nested Organization Follow this structured approach for comprehensive, readable tests: Key Testing Patterns 1. @Nested Classes : Group tests by method being tested 2. @DisplayName : Provide readable test descriptions for test reports 3. Naming Convention : givenX whenY thenZ for clarity 4. AAA Pattern : Explicit // ARRANGE , // ACT , // ASSERT comments 5. @BeforeEach : Setup common test data to reduce duplication 6. assertDoesNotThrow : Test success scenarios without catching exceptions 7. assertThrows : Test exception scenarios with message validation using AssertJ 8. Comprehensive Coverage : Test happy paths, null inputs, edge cases, exceptions 9. Verify Interactions : Use Mockito verify() to ensure methods are called correctly 10. Never Verify : Use never() to ensure methods are NOT called in error scenarios Testing Camel Routes Testing Event Services Testing CompletableFuture Resource Layer Tests (REST Assured) Integration Tests with Real Database Coverage with JaCoCo Maven Configuration (Complete) Run tests with coverage: Test Dependencies Best Practices Test Organization Use @Nested classes to group tests by method being tested Use @DisplayName for readable test descriptions visible in reports Follow givenX whenY thenZ naming convention for test methods Use @BeforeEach for common test data setup to reduce duplication Test Structure Follow AAA pattern with explicit comments ( // ARRANGE , // ACT , // ASSERT ) Use assertDoesNotThrow for success scenarios Use assertThrows for exception scenarios with message validation Verify exception messages match expected values using AssertJ contains() or isEqualTo() Test Coverage Test happy paths for all public methods Test null input handling Test edge cases (empty collections, boundary values, negative IDs, blank strings) Test exception scenarios comprehensively Mock all external dependencies (repositories, services, Camel endpoints) Aim for 80%+ line coverage, 70%+ branch coverage Assertions Prefer AssertJ ( assertThat ) over JUnit assertions for value checks Use fluent AssertJ API for readability: assertThat(list).hasSize(3).contains(item) For exceptions: use JUnit assertThrows to capture, then AssertJ to validate the message For non throwing success paths: use JUnit assertDoesNotThrow For collections: extracting() , filteredOn() , containsExactly() Testing Integration Use @QuarkusTest for integration tests Use @InjectMock to mock dependencies in Quarkus tests Prefer REST Assured for API testing Use @TestProfile for test specific configuration Event Driven Testing Test Camel routes with AdviceWith and MockEndpoint Use @CamelQuarkusTest annotation (if using standalone Camel tests) Verify message content, headers, and routing logic Test error handling routes separately Mock external systems (RabbitMQ, S3, databases) in unit tests Camel Route Testing Use MockEndpoint for asserting message flow Use AdviceWith to modify routes for testing (replace endpoints with mocks) Test message transformation and marshalling Test exception handling and dead letter queues Testing Async Operations Test CompletableFuture success and failure scenarios Use .join() in tests to wait for async completion Test exception propagation from CompletableFuture Verify LogContext propagation to async operations Performance Keep tests fast and isolated Run tests in continuous mode: mvn quarkus:test Use parameterized tests ( @ParameterizedTest ) for input variations Build reusable test data builders or factory methods Quarkus Specific Stay on latest LTS version (Quarkus 3.x) Test native compilation compatibility periodically Use Quarkus test profiles for different scenarios Leverage Quarkus dev services for local testing Use @InjectMock instead of @MockBean (Quarkus specific) Verification Best Practices Always verify interactions on mocked dependencies Use verify(mock, never()) to ensure methods are NOT called in error scenarios Use argThat() for complex argument matching Verify the order of calls when it matters: InOrder from Mockito

quarkus-tdd