Unit Testing: Principles, Practices, and Patterns

A Practical Look at Unit Testing Beyond Coverage Numbers

Many developers have been told to write unit tests, but fewer learn how to design tests that stay useful as the codebase evolves. Vladimir Khorikov’s Unit Testing: Principles, Practices, and Patterns shifts the conversation away from hitting arbitrary coverage percentages and toward creating a test suite that produces maximum value with minimum maintenance costs.

The book examines what makes a unit test good or bad, how to distinguish the classical and London schools of testing, and when each approach makes sense. It then dives into the anatomy of a well-structured test, including the familiar AAA pattern, naming guidelines, and parameterized testing techniques that keep tests readable.

Making Your Tests Work for You

Khorikov identifies four pillars of a good unit test: protection against regressions, resistance to refactoring, fast feedback, and maintainability. With these criteria in mind, he shows how mocks can either help or hurt, where test fragility comes from, and how to refactor a sprawling suite into tests that focus on the most important parts of your application.

Expect clear explanations of in-process and out-of-process dependencies, managed versus unmanaged dependencies, and practical rules for deciding when to use mocks. The coverage of integration testing includes testing with databases and mocking best practices that reduce brittleness.

Beyond the Basics: Anti-Patterns and Real-World Guidance

The final section walks through common unit testing anti-patterns, helping you recognize and avoid traps like overly coupled tests, excessive mocking, and tests that don’t actually verify behavior. Throughout the book, the examples are realistic and the guidance is grounded in everyday software development.

If you are looking to build a test suite that genuinely supports refactoring and long-term code health, this ebook offers a focused, actionable framework. It is especially useful for developers working with modern object-oriented languages who want to move beyond superficial testing habits.