The Pester Book

Master PowerShell Testing with Pester 💻

PowerShell automation becomes much more reliable when you can prove each command, function, and script behaves the way you expect. The Pester Book gives readers a focused, practical route into using Pester, the widely adopted testing framework for PowerShell. Adam Bertram draws on years of IT and automation experience to explain not just the mechanics of Pester, but the testing habits that make complex automation projects safer to maintain.

From First Assertions to Advanced Mocking

The book starts with the foundational concepts—describe blocks, assertions, and test cases—before moving into nuanced topics like custom assertion operators, code coverage measurement, and creating dynamic test cases with parameters. Readers learn how to control pending and skipped states, return failed tests as exit codes, and use tagging to organize test runs.

Mocking and Testable Design ⚙️

Mocking can feel confusing, so this guide breaks it down by object type, explores wrapper functions and ScriptMethod approaches, and shows ways to mock commands that resist conventional stubbing. The later chapters emphasize testable design: managing output properly, separating input, execution, and output, and making sure code state stays predictable.

Infrastructure Testing and Practical Recipes 🧪

Beyond unit tests, the book explores infrastructure testing—checking live conditions, installed software, external applications, exit codes, and remote script blocks. The recipe-style sections give concrete patterns you can adapt to your own environment.

Who Should Read This Book

If you write PowerShell scripts and want to catch errors before they hit production, or if you’re responsible for infrastructure automation and need repeatable validation, this book offers a clear path. It’s especially useful for sysadmins, DevOps engineers, and developers who want to strengthen their PowerShell testing skills.

With its LeanPub “Forever Edition,” this guide remains a practical companion as Pester and PowerShell continue to evolve.