Java Unit Testing: Foundational Mocking with JUnit and Mockito

Writing unit tests for complex Java applications often becomes difficult when your classes depend on databases, external APIs, or other unfinished components. Mocking solves this by simulating these external dependencies, allowing you to test your code in absolute isolation. This text-based course guides you from the absolute basics of unit testing terminology to implementing robust mocks in your test suites. You will learn how to design clean, independent tests that run quickly and fail only when your core logic is actually broken. What you'll learn: 1. Understand the core differences between mocks, stubs, fakes, and dummies. 2. Configure JUnit tests to use Mockito for isolating class dependencies. 3. Implement mock behavior using modern Mockito syntax and strict stubbing. 4. Verify method interactions and capture arguments to ensure correct behavior. 5. Apply mocking best practices to modern Java features like records. 6. Avoid common testing anti-patterns that lead to brittle and hard-to-maintain tests. You will start with foundational definitions of test doubles and unit testing concepts before moving into practical, step-by-step written guides on writing and configuring your first mocks. This course is designed for beginner Java developers and QA engineers who want to improve their testing skills. No prior testing or mocking experience is required. Start reading today to write cleaner, more reliable Java unit tests.