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Testing Java Applications with JUnit 5 and Mockito

Learn JUnit 5 and Mockito by adding tests to a pre-built e-commerce application. Covers unit tests, mocking, MockMvc, @DataJpaTest, TDD, and integration tests with Testcontainers.

Intermediate

17h 31m

14 Lessons

SMU-JAVA-TEST

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About This Course

Build comprehensive test coverage for Java applications using JUnit 5, Mockito, and Spring Boot's testing infrastructure. This course takes a pre-built, untested E-Commerce Order Processing System and adds tests layer by layer: unit tests, Mockito mocks, MockMvc controller tests, repository tests with @DataJpaTest, TDD with a new feature, and full integration tests with Testcontainers. By the capstone you will have a complete, professional-grade test suite.

Course Curriculum

14 Lessons

AI Lesson

Unit Testing Fundamentals and JUnit 5

1h 0m

Learn why testing matters, the test pyramid, JUnit 5 architecture, @Test, @BeforeEach/@AfterEach, Assertions, @DisplayName, @Nested, @ParameterizedTest with @ValueSource and @CsvSource, and test naming conventions.

Lab Exercise

Unit Testing - Lab Exercises

1h 45m 4 Exercises

Hands-on practice writing JUnit 5 unit tests for Order, OrderItem, and Product domain classes in the E-Commerce Order Processing System.

Write Order Domain Unit Tests ~15 min

Test Order.addItem with Multi-Item Total Calculation ~15 min

Write Parameterized Tests for Product.isInStock ~15 min

Run the Full Test Suite with mvn test ~15 min

AI Lesson

Mockito - Mocking Dependencies

1h 0m

Learn why mocking exists, Mockito library, @Mock, @InjectMocks, when/thenReturn, verify, ArgumentCaptor, @Spy, doReturn for void methods, matchers, and strict stubbing.

Lab Exercise

Mockito - Lab Exercises

1h 33m 4 Exercises

Hands-on practice writing Mockito tests for OrderService with mocked OrderRepository and ProductService, using @Mock, @InjectMocks, when/thenReturn, verify, and ArgumentCaptor.

Set Up OrderServiceTest with Mockito Annotations ~12 min

Write createOrder_success with Stubbing and Verify ~12 min

Test Insufficient Stock with verify(never()) ~12 min

Capture Saved Order with ArgumentCaptor ~12 min

AI Lesson

Testing Spring Boot Controllers

45m

Learn how to test Spring Boot REST controllers using @WebMvcTest and MockMvc without starting a real server. Covers @MockBean, perform/andExpect, jsonPath assertions, and testing validation errors and 404 responses.

Lab Exercise

Testing Spring Boot Controllers - Lab Exercises

1h 33m 4 Exercises

Practice writing @WebMvcTest tests for OrderController and ProductController using MockMvc, @MockBean, and jsonPath assertions.

Set Up OrderControllerTest with @WebMvcTest ~12 min

Test GET Order Returns 404 When Not Found ~12 min

Test POST Order Returns 201 Created ~12 min

Write ProductController Tests ~12 min

AI Lesson

Testing the Repository Layer

45m

Learn how to test Spring Data JPA repositories using @DataJpaTest, TestEntityManager, and H2 in-memory database. Covers derived queries, @Query JPQL methods, Pageable, and @Transactional auto-rollback.

Lab Exercise

Repository Layer Testing - Lab Exercises

1h 33m 4 Exercises

Practice writing @DataJpaTest tests for OrderRepository and ProductRepository using TestEntityManager to persist test data and verify query methods.

Set Up OrderRepositoryTest with @DataJpaTest ~12 min

Test findByStatus with Pagination ~12 min

Write ProductRepository Low-Stock Query Test ~12 min

Test findTopSellingProducts Native Query ~12 min

AI Lesson

Test-Driven Development (TDD)

45m

Learn the Red-Green-Refactor TDD cycle: writing failing tests first, implementing the minimum code to make them pass, then refactoring. Covers triangulation, @Disabled, and when TDD is and is not the right approach.

Lab Exercise

Test-Driven Development - Lab Exercises

1h 33m 4 Exercises

Practice the TDD Red-Green-Refactor cycle by building DiscountService test-first: write failing tests, implement minimum code to pass, then refactor.

RED Phase: Write the First Failing Test ~12 min

GREEN Phase: Implement the Threshold Check ~12 min

Triangulate: PREMIUM Tier and Refactor ~12 min

Boundary Tests and Full Suite Verification ~12 min

AI Lesson

Integration Testing with @SpringBootTest

45m

Learn how to write full-stack integration tests using @SpringBootTest, TestRestTemplate, and Testcontainers for real PostgreSQL. Covers WebEnvironment options, @Transactional rollback in tests, @ActiveProfiles, and @Sql fixtures.

Lab Exercise

Integration Testing - Lab Exercises

1h 34m 4 Exercises

Practice writing @SpringBootTest integration tests using TestRestTemplate and Testcontainers PostgreSQL to test the full order lifecycle end-to-end.

Set Up OrderIntegrationTest with @SpringBootTest ~12 min

Test Full Order Creation with Items ~12 min

Add Testcontainers PostgreSQL ~15 min

Test Invalid Product Returns 404 ~10 min

AI Lesson

Capstone Briefing: Building a Complete Test Suite

30m

Review all test types from the course and receive your capstone assignment: write the complete test suite for the ReturnOrder feature (ReturnOrderService, ReturnOrderController, ReturnOrderRepository) across all five test layers.

Lab Exercise

Capstone Project: Testing the ReturnOrder Feature

2h 30m 6 Exercises

Write the complete test suite for the ReturnOrder feature covering all test layers: unit tests, Mockito service tests, @WebMvcTest controller tests, @DataJpaTest repository tests, and @SpringBootTest integration tests.

Unit Tests for ReturnOrder Domain Logic ~15 min

Mockito Tests for ReturnOrderService ~20 min

@WebMvcTest for ReturnOrderController ~20 min

@DataJpaTest for ReturnOrderRepository ~15 min

@SpringBootTest Integration Test for Return Lifecycle ~20 min

Stretch Goal: Code Coverage with JaCoCo ~15 min

This course includes:

24/7 AI Instructor Support
Live Lab Environments
7 Hands-on Lessons
6 Months Access
Completion Badge
Certificate of Completion

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Complete all lessons to unlock the Java Testing with JUnit and Mockito achievement badge.

Testing Java Applications with JUnit 5 and Mockito

About This Course

Course Curriculum

Unit Testing Fundamentals and JUnit 5

Unit Testing - Lab Exercises

Mockito - Mocking Dependencies

Mockito - Lab Exercises

Testing Spring Boot Controllers

Testing Spring Boot Controllers - Lab Exercises

Testing the Repository Layer

Repository Layer Testing - Lab Exercises

Test-Driven Development (TDD)

Test-Driven Development - Lab Exercises

Integration Testing with @SpringBootTest

Integration Testing - Lab Exercises

Capstone Briefing: Building a Complete Test Suite

Capstone Project: Testing the ReturnOrder Feature

This course includes:

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Java Testing with JUnit and Mockito

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