This book explains in detail how to implement unit tests using two very popular open source Java technologies: JUnit and Mockito. It presents a range of techniques necessary to write high quality unit tests - e.g. mocks, parametrized tests and matchers. It also discusses trade-offs related to the choices we have to make when dealing with some real-life code issues.

The book stresses the importance of writing readable and maintainable unit tests, and puts a lot of stress on code quality. It shows how to achieve testable code and to eliminate common mistakes by following the Test Driven Development approach. Every topic discussed in the book is illustrated with code examples, and each chapter is accompanied by some exercises.

By reading this book you will:

Grasp the role and purpose of unit tests

Write high-quality, readable and maintainable unit tests

Learn how to use JUnit and Mockito (but also other useful tools)

Avoid common pitfalls when writing unit tests

Recognize bad unit tests, and fix them in no time

Develop code following the Test Driven Development (TDD) approach

Use mocks, stubs and test-spies intelligently

Measure the quality of your tests using code coverage and mutation testing

Learn how to improve your tests' code so it is an asset and not a burden

Test collections, expected exceptions, time-dependent methods and much more

Customize test reports so that they show you what you really need to know

Master tools and techniques your team members have never even heard of (priceless!) :)

Nowadays every developer is expected to write unit tests. While simple in theory, in practice writing high-quality unit tests can turn out to be a real challenge. This book will help.

Tomek Kaczanowski is a technical team leader from Krakow, Poland. He has a strong interest in code quality, testing and automation - preferably all three together. Combining technical with soft skills, he also ventures into the realms of mentoring, teaching, lecturing and article writing, not to mention preaching sermons to the unconverted in the hope of redeeming them (or at least their code)! He hates doing things manually, and is allergic to empty src/test/java directories. Tomek believes that by working with legacy code, and improving it, he can make the world a better place. To his disappointment, the world does not seem to care all that much about his efforts. Apart from all this weirdness, he is a pretty normal person – a husband, father of two, and cat owner.