Welcome to our lesson on eliminating duplicated code and enhancing maintainability through method extraction and refactoring magic numbers. Writing clean and maintainable code is crucial in modern software development, and refactoring is a key practice that helps achieve these goals. This lesson focuses on identifying duplicate code segments and restructuring them to improve readability and maintainability.

We will follow a TDD (Test-Driven Development) approach using ScalaTest, ensuring that our functionality remains intact as we refactor code to a cleaner form.

This lesson picks up from an existing ShoppingCart example to concentrate on the Refactor step of the Red-Green-Refactor cycle. Let's dive into identifying and refactoring duplicated code to enhance the codebase's quality.

Before we delve into specific "smells," it's important to understand what "code smells" are. Code smells are indicators in the code suggesting deeper problems, such as poorly structured code or potential defects, though they aren't bugs themselves. Common examples include duplicate code, long methods, and magic numbers. These signals can hinder code readability and maintainability and may eventually lead to significant issues.

Refactoring patterns provide structured techniques to address these code smells, improving the overall quality of the codebase while maintaining its behavior. By employing these patterns, we can systematically transform problematic sections into cleaner, more efficient code. In this lesson, we'll target duplications by leveraging refactoring patterns, such as method extraction and refactoring magic numbers, to enhance the clarity and adaptability of our code. We can rely on our tests to ensure we don't break any existing functionality!