Unit Testing REST APIs with JUnit 5 and Mockito

Writing robust unit tests is a critical skill for modern Java developers, ensuring that your web applications remain stable as they grow. This text-based course guides you through the principles of isolating your code under test, allowing you to catch bugs early in the development lifecycle. You will transition from writing fragile integration tests to crafting fast, deterministic unit tests for your API endpoints. Learn to establish a solid testing foundation starting with core testing terminology, assertions, and test lifecycle phases. Next, explore how to mock complex external dependencies and database interactions to keep your test suite running efficiently. What you will learn: Understand the foundational concepts of unit testing and test-driven development; Configure JUnit 5 test lifecycles and write expressive assertions; Mock service dependencies and database layers using Mockito annotations; Verify behavior, method execution order, and handle exceptional cases; Apply modern testing practices including parameterization and assertion libraries. You will begin with basic setup and testing concepts before advancing to real-world API mocking patterns and dependency verification. This course is designed for beginner to intermediate Java developers who want to improve their testing skills, with no prior unit testing experience required. Start writing cleaner, more maintainable Java code today.