Effective Unit Testing with Mocks, Stubs, and Test Doubles

Writing robust unit tests requires isolating the code you are testing from external factors like databases, APIs, or complex internal dependencies. This course teaches the foundational techniques required to achieve that essential isolation. By the end of this course, you will master the principles of dependency isolation and confidently apply different types of test doubles—including mocks, stubs, and spies—to verify application behavior reliably and efficiently. What you'll learn: * Understand the core taxonomy of test doubles: Dummies, Fakes, Stubs, Spies, and Mocks. * Learn how to define clear interfaces and boundaries in your code to enable effective dependency injection and mocking. * Practice creating and configuring stubs to control return values and simulate specific application states. * Apply mocks to verify interactions and behavior, ensuring your code handles external calls correctly. * Master techniques for isolating complex dependencies and handling asynchronous operations or side effects during testing. * Configure test setups to efficiently manage the lifecycle and cleanup of your test doubles. The course begins by defining the core concepts and the need for dependency isolation in high-quality testing. We then move into practical, text-based exercises demonstrating the creation and application of each type of test double in common unit testing scenarios. This course is designed for beginner developers and QA professionals who have basic familiarity with writing code and want to learn best practices for modern unit testing. No prior experience with advanced mocking frameworks is required. Start writing higher quality, more focused tests today.