The Pester Book (Pester Book (Forever Edition))
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The Pester Book

About the Book

"Pester is an important skill that every PowerShell user should master."
- Jeffrey Snover, Creator of PowerShell

Pester is a unit-testing framework for PowerShell, and perhaps the first open-source software product that ships with Windows itself! Author Adam Bertram will walk you through the Pester philosophy, syntax, and numerous real-world examples.

We'll cover everything you need to know from knowing nothing about Pester and testing PowerShell scripts to becoming a testing master!

Part 1 covers the core syntax of Pester and introduces you to various possible use cases for the different syntax elements. It's enough to get you up and running if you're familiar with unit testing, or if you want to give Pester a spin.

Part 2 will take that syntax and dig into the world of unit testing and test-driven development, through a series of real-world walkthroughs. Some of these will be "stream of consciousness," following the actual process someone might use to add or develop Pester tests. This part will also cover using Pester for infrastructure validation in an "infrastructure from code" environment.

Part 3 will introduce you to Gherkin. Gherkin is another style of test writing that comes with Pester. This part will introduce you to Gherkin, how it's different than Pester test design and how it integrates with Pester.

Part 4 will tackle code coverage, an important topic to help make sure you're testing all of your code but with some not-so-obvious gotchas, you need to watch out for.

Part 5 will be more of a "cookbook," with recipes for testing specific types of situations. You will find many different, specific use-cases in here and how to test for them.

Check Out the Free Sample

The free sample includes sample chapters, but why bother? LeanPub has a no-questions-asked refund policy, so it's completely risk-free to grab the "real" book and see what you think.

What Formats are Available?

All LeanPub books are offered in PDF, MOBI, and EPUB, and you get all three with your purchase. Note that the PDF is probably the "highest fidelity" version, especially in terms of code listings.


I use The Pester Book to on-board all my new members, so they start with a solid foundation in Pester and how it is used to test infrastructure and powershell module code. In addition to providing the go-to resource for booting up on Pester, I find myself referring back to it often as a reference for some of the more advanced Pester concepts that I need to solve some of our more complex testing scenarios
Brett Hinton

The Pester book is invaluable as standard reference for getting to grips with the Pester concepts as PowerShell testing framework, as well as providing practical examples of how to automate testing your PowerShell code.
Michel de Rooij

If you want to prove your PowerShell scripts are actually doing what they are supposed to, this book is for you. The Pester Book by Adam Bertram will teach you how to utilize Pester for testing your PowerShell code in ways you never thought you could do without trial and error. You’ll learn how to leverage the Pester framework to mock data that can be used to verify your functions, perform infrastructure testing, and much more. This book is one of my favorites and sits next to many other PowerShell books I’ve bought over the years. The Pester Book helped take my scripts to the next level.
Bill Kindle

The Pester book not only gave me an in-depth understanding of the Pester framework; it also taught me a new way of looking at my PowerShell code. The end result was cleaner, more concise code with unit tests to back it up.
Monte Hazboun
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About the Author

Adam Bertram
Adam Bertram

Adam Bertram is a 20+ year veteran of IT and an experienced online business professional. He’s a consultant, Microsoft MVP, blogger, trainer, published author and content marketer for multiple technology companies. Catch up on Adam’s articles at, connect on LinkedIn, or follow him on Twitter at @adbertram.

Bundles that include this book

3 Books
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Reader Testimonials

Nicholas Getchell
Nicholas Getchell

I just finished this book last night. I've been using Pester for a while but still earned a ton.

Table of Contents

  • About This Book
  • About the Author
  • Foreword
  • Feedback
  • Code Samples
  • Introduction
    • Testing as Institutional Memory
    • Testing Drives Better Modularization
    • Tests as Functional Specifications
    • Tests in Automated Build Pipelines
    • Where We’re Not Going
    • Resources
  • Part I - Pester Concepts
  • Block Introduction
    • Describe Blocks
    • Context Blocks
    • It Blocks
    • Before and After Blocks
    • Summary
  • TestDrive and TestRegistry
    • Using TestDrive
    • Using TestRegistry
    • Summary
  • Assertions
    • Using the Should Assertion
    • Understanding Should Operators
    • Testing Collections
    • Other Tests
    • Testing Errors
    • Adding Custom Assertion Operators
    • Because
    • Summary
  • Test Cases
    • Creating Tests for Different Parameters
    • Using the TestCases Parameter
    • Using the Test Name Token
    • Summary
  • Mocking Introduction
    • Mock Walkthrough
    • Mock Assertions
    • Summary
  • Code Coverage
    • Why Code Coverage?
    • Using Pester to Measure Code Coverage
    • Getting Granular with Code Coverage
    • Summary
  • Gherkin
    • Files
    • Features
    • Scenarios
    • Steps
    • Step Definitions
    • Running Gherkin Tests
    • Summary
  • Part 2: Using Pester
  • Controlling Test Results
    • Pending and Skipped States
    • Forcing Pass/Fail States
    • Summary
  • Working with Pester Output
    • nUnit XML
    • Returning Failed Tests as Exit Codes
    • Summary
  • Tagging
    • Introduction to Tagging
    • Tagging Strategies
    • Summary
  • Modules and Dot-Sourced Script Gotchas
    • Scripts with Functions
    • Modules
    • Summary
  • Advanced Mocking
    • Mocking Specific Object Types
    • Mock Scope
    • Module-Level Mocks
    • Parameter Filters
    • Summary
  • Mocking the Unmockable
    • .NET Methods
    • Creating Wrapper Functions
    • “Overwriting” .NET Methods with a ScriptMethod
    • Using “Stubbed” Commands
    • Asserting Mocks “Transitively”
    • Summary
  • Improving Code Coverage
    • Step #1: Getting a Baseline
    • Step #2: Build the Test Framework
    • Step #3: Create the Mocks
    • Step #4: Know the “Before” Code Coverage
    • Step #5: Build all Tests
    • Step #6: Re-check Code Coverage
    • Summary
  • Infrastructure Testing
    • Analyzing the Code
    • Getting Testing Dependencies in Place
    • Prototyping the Infrastructure Tests
    • Assessing the Current Environment
    • Writing the Infrastructure Tests
    • Dependencies
    • Operational Validation Framework (OVF)
    • Summary
  • Troubleshooting and Debugging
    • Sending Variables to the Console with Write-Host
    • Using Debugger Breakpoints During Tests
    • Summary
  • Test Walkthrough #1
    • Analyzing the Code
    • Refactoring
    • Deciding What to Test
    • Find the Shortest Code Path
    • Creating Test(s) for the Shortest Code Path
    • Building Tests for Other Code Paths
    • Summary
  • Test Walkthrough #2
    • Understand the Subject
    • Designing Tests
    • Writing the Tests
    • ImportVariables Parameter
    • ImportModules Parameter
    • RunspaceTimeout Parameter
    • Parameter parameter
    • Summary
  • Part 3: Hands-On Design and Testing
  • Buildling Testable Code
    • Modularization
    • Limit Function Input
    • Input Via Parameters
    • Managing Output Properly
    • Summary
  • Test Design Practices
    • Ensuring Code “State” Doesn’t Change
    • The Input/Execution/Output Pattern
    • Choosing When to Create Describe Blocks
    • Naming Conventions
    • Summary
  • Part 4: Pester Cookbook
  • Recipe: Testing for Live Conditions
  • Recipe: Testing for Installed Software
  • Recipe: Ensuring all Functions in a Module Have Tests
  • Recipe: Testing External Applications
    • The Background
    • Testing Exit Codes from Standalone EXE files
  • Recipe: Testing Syntax
  • Recipe: Testing Remote Script Blocks
  • Resources
    • Video Courses
    • Articles
  • Release Notes

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