The return of the famous bestseller. Elegant, flexible and understandable code that is easy to modify, that works correctly and that does not throw unpleasant surprises at its creators. Is this really possible? To achieve your goal, try testing the program before it is written. It is this paradoxical idea that forms the basis of the TDD (Test-Driven-Development) methodology. Nonsense? Don't rush to jump to conclusions. Considering the use of TDD using the example of developing real program code, the author demonstrates the simplicity and power of this technique. The book contains two software projects that were entirely implemented using TDD. The examples are followed by an extensive catalog of TDD-style techniques, patterns, and refactorings relevant to TDD. The book will be useful for any programmer who wants to increase their productivity and enjoy programming.