Unit Testing with JUnit

Learn how to create tests that adapt to specific scenarios or run across varied input data without duplication. You’ll see how conditional tests can be triggered based on operating system, system properties, or environment variables, ensuring relevance to the execution context. Parameterised tests will also be explored, showing how a single method can validate multiple data sets, improving coverage, reducing redundancy, and keeping your test suite lean and efficient. 

Discover how to isolate the code under test by replacing complex or unpredictable dependencies with controlled substitutes. This module clarifies the differences between stubs, mocks, and spies, and demonstrates when to use each. You’ll practise using Mockito to set expectations, verify interactions, and simulate behaviours, allowing you to test in a stable, repeatable environment without relying on external systems or real-world conditions. 

Tackle the intricacies of testing more demanding Java components such as IO operations, servlets, and multi-threaded applications. You’ll learn strategies for managing transaction rollbacks in DAO testing, simplifying servlet testing by extracting business logic, and addressing the challenges of concurrent code. Best practices for reducing flakiness in non-deterministic tests are also covered, enabling you to maintain accuracy and reliability even under complex conditions. 

Explore how TDD can transform both the way you write code and the quality of the software you produce. You’ll follow the Red-Green-Refactor cycle, using tests to shape design decisions and encourage simpler, cleaner solutions. This approach not only increases confidence that your code works as intended but also helps prevent regressions, making it easier to extend and maintain applications over time.