Pester Testing Self Contained Scripts

2021-01-08T20:26:05+00:00

param([switch]$Testing)

function Get-Name {
[CmdletBinding()]
param(
[String]$Name = ‘you’
)

‘Hello, {0}’ -f $Name
}

if(!$Testing){Get-Name -Name Shane}

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2019-02-22T05:54:23+00:00

Thanks for the article 🙂 That invoke expression is just for the demo, in real life you’d use just an empty function. I’ll clean it up and publish it as a module. And add it to Pester v5. It already does a similar thing with Add-Dependency.

I like your approach with ast as well, but I think it won’t work when you use $PSScriptRoot in your script.

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	using namespace System.Management.Automation
	using namespace System.Management.Automation.Language
	using namespace System.Reflection

	function Get-FunctionInfo {
	<#
	.SYNOPSIS
	Get an instance of FunctionInfo.
	.DESCRIPTION
	FunctionInfo does not present a public constructor. This function calls an internal / private constructor on FunctionInfo to create a description of a function from a script block or file containing one or more functions.
	.PARAMETER IncludeNested
	By default functions nested inside other functions are ignored. Setting this parameter will allow nested functions to be discovered.
	.PARAMETER Path
	The path to a file containing one or more functions.
	.PARAMETER ScriptBlock
	A script block containing one or more functions.
	.INPUTS
	System.String
	.OUTPUTS
	System.Management.Automation.FunctionInfo
	.EXAMPLE
	Get-ChildItem -Filter *.psm1 \| Get-FunctionInfo

	Get all functions declared within the *.psm1 file and construct FunctionInfo.
	.EXAMPLE
	Get-ChildItem C:\Scripts -Filter *.ps1 -Recurse \| Get-FunctionInfo

	Get all functions declared in all ps1 files in C:\Scripts.
	.NOTES
	Change log:
	10/12/2015 – Chris Dent – Improved error handling.
	28/10/2015 – Chris Dent – Created.
	#>

	[CmdletBinding(DefaultParameterSetName = 'FromPath')]
	[OutputType([System.Management.Automation.FunctionInfo])]
	param (
	[Parameter(Position = 1, ValueFromPipelineByPropertyName = $true, ParameterSetName = 'FromPath')]
	[Alias('FullName')]
	[String]$Path,

	[Parameter(ParameterSetName = 'FromScriptBlock')]
	[ScriptBlock]$ScriptBlock,

	[Switch]$IncludeNested
	)

	begin {
	$executionContextType = [PowerShell].Assembly.GetType('System.Management.Automation.ExecutionContext')
	$constructor = [FunctionInfo].GetConstructor(
	[BindingFlags]'NonPublic, Instance',
	$null,
	[CallingConventions]'Standard, HasThis',
	([String], [ScriptBlock], $executionContextType),
	$null
	)
	}

	process {
	if ($pscmdlet.ParameterSetName -eq 'FromPath') {
	try {
	$scriptBlock = [ScriptBlock]::Create((Get-Content $Path –Raw))
	} catch {
	$ErrorRecord = @{
	Exception = $_.Exception.InnerException
	ErrorId = 'InvalidScriptBlock'
	Category = 'OperationStopped'
	}
	Write-Error @ErrorRecord
	}
	}

	if ($scriptBlock) {
	$scriptBlock.Ast.FindAll( {
	param( $ast )

	$ast -is [FunctionDefinitionAst]
	},
	$IncludeNested
	) \| ForEach-Object {
	try {
	$internalScriptBlock = $_.Body.GetScriptBlock()
	} catch {
	Write-Debug $_.Exception.Message
	}
	if ($internalScriptBlock) {
	$constructor.Invoke(([String]$_.Name, $internalScriptBlock, $null))
	}
	}
	}
	}
	}

	describe 'testing our function with scriptroot' {
	# Get our self contained script info.
	. .\Get-FunctionInfo.ps1
	$fInfo = Get-FunctionInfo –Path .\Get-NameScriptBlock.ps1

	# Create something we can dot-source.
	$Fake = "function $($fInfo.Name) { $($fInfo.Definition) }"
	$FakeFunc = [scriptblock]::Create($Fake)
	. $FakeFunc

	Context 'Results' {
	It 'should have the expected default result' {
	Get-Name \| Should –Be 'Hello, you. Script root is C:\Users\shane.oneill\Git\Blog'
	}

	It 'should have the expected result for passed in values' {
	Get-Name –Name 'Shane' \| Should –Be 'Hello, Shane. Script root is C:\Users\shane.oneill\Git\Blog'
	}
	}
	}

Pester Testing Self Contained Scripts

I’m going to (optimistically) say that you are all Pester testing your scripts.

The first few lines of a Pester “.tests.ps1” file…

Where things differ…

PSPowerHour

AST

Our Self Contained Script

Now we can test it!

UPDATE: 2019-02-22.

Now if you’ll excuse me…

Like this:

Author: Shane O'Neill

7 thoughts on “Pester Testing Self Contained Scripts”

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	$here = Split-Path –Parent $MyInvocation.MyCommand.Path
	$sut = (Split-Path –Leaf $MyInvocation.MyCommand.Path) -replace '\.Tests\.', '.'
	. "$here\$sut"

	function Get-Name {
	[CmdletBinding()]
	param(
	[String]$Name = 'you'
	)

	'Hello, {0}. Script root is {1}' -f $Name, $PSScriptRoot
	}

	Get-Name –Name Shane