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

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Completed on 2019-06-24

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.

How Can I Contact the Author?

I love feedback. Use the "Email the Author" link, just below, to contact me or feel free to reach out to me on Twitter @adbertram. For feedback on the book, please provide a chapter, heading, and short snippet of text to let me know where you're looking - page numbers don't do any good, as they don't correspond with our source files.

About the Author

Adam Bertram
Adam Bertram

Adam Bertram is a 20-year veteran of IT and experienced online business professional. He’s an entrepreneur, IT influencer, Microsoft MVP, blogger, trainer and content marketing writer for multiple technology companies. Adam is also the founder of the popular IT career development platform TechSnips. Catch up on Adam’s articles at, connect on LinkedIn, or follow him on Twitter at @adbertram or the TechSnips Twitter account at @techsnips_io.

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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