Book Image

Get Your Hands Dirty on Clean Architecture

By : Tom Hombergs
Book Image

Get Your Hands Dirty on Clean Architecture

By: Tom Hombergs

Overview of this book

Building for maintainability is key to keeping development costs low and processes easy. The second edition of Get Your Hands Dirty on Clean Architecture is here to equip you with the essential skills and knowledge to build maintainable software. With this comprehensive guide, you’ll explore the drawbacks of conventional layered architecture and the advantages of domain-centric styles such as Robert C. Martin's Clean Architecture and Alistair Cockburn's Hexagonal Architecture. Then, you’ll dive into hands-on explanations on how to convert hexagonal architecture into actual code. You'll learn in detail about different mapping strategies between the layers of hexagonal architecture and discover how to assemble the architectural elements into an application. Additionally, you’ll understand how to enforce architecture boundaries, which shortcuts produce what types of technical debt, and how, sometimes, it is a good idea to willingly take on those debts. By the end of this second edition, you'll be armed with a deep understanding of the hexagonal architecture style and be ready to create maintainable web applications that save money and time.
Table of Contents (13 chapters)

Testing a Domain Entity with Unit Tests

We will start by looking at a domain entity at the center of our architecture. Let's recall the Account entity from Chapter 4, Implementing a Use Case. The state of an Account consists of a balance the account had at a certain point in the past (the baseline balance) and a list of deposits and withdrawals (activities) since then. We now want to verify that the withdraw() method works as expected:

class AccountTest {


  void withdrawalSucceeds() {

    AccountId accountId = new AccountId(1L);

    Account account = defaultAccount()



        .withActivityWindow(new ActivityWindow(