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

Throughout this course, we will be using C++, a powerful object-oriented programming language known for its performance and versatility. We will employ Google Test, a widely-used testing framework, to facilitate test-driven development (TDD), along with Google Mock, a valuable tool for creating mock objects during testing.

This lesson builds upon an existing ShoppingCart example to dive into the Refactor step of the Red-Green-Refactor cycle. Let's begin by identifying and refactoring duplicated code to improve the quality of the codebase.

Before we proceed to 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. Trust in your tests to ensure existing functionality remains unaffected!