Book Image

Get Your Hands Dirty on Clean Architecture - Second Edition

By : Tom Hombergs
4 (1)
Book Image

Get Your Hands Dirty on Clean Architecture - Second Edition

4 (1)
By: Tom Hombergs

Overview of this book

Building for maintainability is key to keep development costs low (and developers happy). 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. Building upon the success of the first edition, this comprehensive guide explores the drawbacks of conventional layered architecture and highlights the advantages of domain-centric styles such as Robert C. Martin's Clean Architecture and Alistair Cockburn's Hexagonal Architecture. Then, the book dives into hands-on chapters that show you how to manifest a Hexagonal Architecture in actual code. You'll learn in detail about different mapping strategies between the layers of a Hexagonal Architecture and see how to assemble the architecture elements into an application. The later chapters demonstrate how to enforce architecture boundaries, what 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. Whether you're a seasoned developer or a newcomer to the field, "Get Your Hands Dirty on Clean Architecture" will empower you to take your software architecture skills to new heights and build applications that stand the test of time.
Table of Contents (18 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 5, Implementing a Use Case. The state of Account consists of a balance an account had at a certain point in the past (the baseline balance) and a list of deposits and withdrawals (activities) made since then.

We now want to verify that the withdraw() method works as expected:

The preceding test is a plain unit test that instantiates an Account in a specific state, calls its withdraw() method, and verifies that the withdrawal was successful and had the expected side effects on the state of the Account object under test.

The test is rather easy to set up, is easy to understand, and runs very fast. Tests don’t come much simpler than this. Unit tests such as these are our best bet to verify the business rules encoded within our domain entities. We don’t need any other type...