Part 2 introduces the techniques necessary for effective TDD. Along the way, we will incrementally build the core logic of a word guessing game, Wordz – writing all our tests first.

By the end of this part, we will have produced high-quality code by writing tests first. The SOLID principles and hexagonal architecture will help us organize code into well-engineered building blocks that are easy to test. Test doubles will bring external dependencies under our control. We will look at the bigger picture of test automation and how the test pyramid, QA engineers, and workflow improve our work.

This part has the following chapters:

• Chapter 4, Building an Application Using TDD
• Chapter 5, Writing Our First Test
• Chapter 6, Following the Rhythms of TDD
• Chapter 7, Driving Design – TDD and SOLID
• Chapter 8, Test Doubles – Stubs and Mocks
• Chapter 9, Hexagonal Architecture – Decoupling External Systems
• Chapter 10, FIRST Tests and the Test Pyramid
• Chapter 11, How TDD Fits into Quality Assurance
• Chapter 12, Test First, Test Later, Test Never