The Art Of Unit Testing, Second Edition -

The book clears the fog around isolation patterns. It teaches you exactly when to use a Stub (to provide data) versus a Mock (to verify behavior), helping you avoid over-specifying tests that break with every minor refactor.

by Roy Osherove is a definitive guide for developers looking to master the craft of writing maintainable, trustworthy, and effective tests. While the first edition laid the groundwork, this version pivots to real-world complexities, focusing on the social and technical challenges of testing legacy code and managing large test suites. Key Features The Art of Unit Testing, Second Edition

While examples primarily use C# , the principles are designed to be universally applicable to Java, JavaScript, Python, and other object-oriented languages. The book clears the fog around isolation patterns