PowerShell-Scripts/Learning_Pester.dib at main · BaileyFurrow/PowerShell-Scripts · GitHub

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#!meta

{"kernelInfo":{"defaultKernelName":"pwsh","items":[{"aliases":[],"languageName":"pwsh","name":"pwsh"}]}}

#!markdown

## Pester Basics

Must be installed to use. Install using:

#!pwsh

Install-Module -Name Pester

#!markdown

### A Pester File

Pester test scripts are just PowerShell files ending in `.Tests.ps1`.

Each Pester file contains one or more `describe` blocks that each contain zero or more `context` blocks that contain one or more `it` blocks that contain assertions.

#!value

describe
|
|-context
  |
  |-it
    |
    |-assertions

#!markdown

### `describe` Block

Groups like tests together.

Syntax is a name in 'single quotes' followed by a script block:

#!pwsh

Describe 'IIS' {
}

#!markdown

### `context` Block

The `context` block is optional.

It groups similar `it` blocks together.

#!pwsh

Describe 'IIS' {
    Context 'Windows features' {
    }
}

#!markdown

### `it` Blocks

Smaller component that labels the actual test to run.

#!pwsh

Describe 'IIS' {
    Context 'Windows features' {
        It 'installs the Web-Server Windows feature' {
        }
    }
}

#!markdown

### Assertions

`it` blocks must include one or more assertions.

*Assertions* are the actual test to be ran.

Most common assertion is `Should`, with different operators, such as `-be`, `-bein`, `-belessthan`, etc.

[Full list can be found here.](https://github.com/pester/Pester/wiki/)

#!pwsh

# Note - this will fail bc there is no `Get-WIndowsFeature` command.
Describe 'IIS' {
    Context 'Windows features' {
        It 'installs the Web-Server Windows feature' {
            $parameters = @{
                ComputerName = 'WEBSRV1'
                Name = 'Web-Server'
            }
            (Get-WindowsFeature @paarmeters).Installed | Should -Be $true
        }
    }
}

#!markdown

## Learn More

Learn more about Pester from [The Pester Book](https://leanpub.com/pesterbook/) or from [4sysops articles on Pester](https://4sysops.com/archives/powershell-pester-testing-getting-started/).