In previous lessons, we've explored the fundamentals of Test Driven Development (TDD), specifically the Red-Green-Refactor cycle and the setup of a testing environment using Java and JUnit. Now, we shift our focus to a key aspect of TDD: managing dependencies. Managing dependencies ensures that each unit of your application can be tested in isolation, which is crucial in TDD for maintaining code reliability and robustness.

In this lesson, we will examine how to use interfaces for abstraction in Java, allowing us to manage dependencies effectively. Using simple examples, we will demonstrate how to apply the Red-Green-Refactor cycle in this context. We'll use Java with JUnit, a widely used framework in testing, to provide practical context. Let’s dive in.

Dependencies in software development refer to the components or systems that a piece of code relies on to function properly. In the context of testing, dependencies can complicate unit tests because they might introduce external factors that affect the test outcomes. To ensure tests are isolated and independent, we use abstractions.

An interface in Java acts as a contract that defines the methods a class should implement. By programming against interfaces, you can easily swap out implementations, making code more modular and test-friendly.

For example, consider a logger that a component uses to record actions. By abstracting the logger as an interface, you decouple the component from a specific logging implementation. This abstraction allows you to replace the actual logger with a mock or stub when testing, thus focusing on testing the component, not its dependencies.