Introduction to Testing in Java

Overview

Learn how to write effective tests in Java using JUnit and Mockito to build robust, reliable applications with confidence.

Why Testing Matters

Testing is one of the most important skills that separates beginners from professional software engineers. In the real world, especially in enterprise environments, any code that is not tested is assumed to be broken. Testing is not an optional step - it is a fundamental responsibility of software engineers and a key part of maintaining robust and resilient Java applications. Java is widely known for its stability and reliability, and testing plays a major role in upholding these qualities.

What You Will Learn

This course will guide you through the core concepts of software testing in Java. You will start by learning about the most common types of tests and how they are used to improve code quality and application behavior. You will gain hands-on experience with JUnit, the most widely used testing framework in the Java ecosystem, and learn how to simulate complex testing scenarios using Mockito. As you progress, you will apply the methodology of Test Driven Development and learn to write both parameterized and integration tests. By the end of the course, you will have the tools and techniques you need to confidently write meaningful tests that ensure your code is reliable, maintainable, and production-ready.

Syllabus

Foundations of Testing

Start by exploring automated software testing and the typical pitfalls it helps avoid. Then, gain hands-on experience with Java's JUnit 5 library and learn to structure and write unit tests.

Testing with Dependencies

Examine how software components interact and rely on each other, and see how integration testing verifies these interactions by testing a class alongside its dependencies. This chapter then introduces mocking as a method to simulate dependencies and focus testing on the logic being evaluated.

Further techniques and annotations

Explore multiple ways to make testing less verbose. One way to do so is parameterizing tests; another is using the @BeforeEach annotation. Finally, it presents a new way to think about testing.