Remove built-in version of Pester 3 (or -All) from Windows 10 Program Files and Program Files (x86).

Uninstall-Pester.ps1

#Requires -RunAsAdministrator

function Uninstall-Pester ([switch]$All) {
    if ([IntPtr]::Size * 8 -ne 64) { throw "Run this script from 64bit PowerShell." }

    #Requires -RunAsAdministrator
    $pesterPaths = foreach ($programFiles in ($env:ProgramFiles, ${env:ProgramFiles(x86)})) {
        $path = "$programFiles\WindowsPowerShell\Modules\Pester"
        if ($null -ne $programFiles -and (Test-Path $path)) {
            if ($All) { 
                Get-Item $path
            } 
            else { 
                Get-ChildItem "$path\3.*" 
            }
        }
    }


    if (-not $pesterPaths) {
        "There are no Pester$(if (-not $all) {" 3"}) installations in Program Files and Program Files (x86) doing nothing."
        return
    }

    foreach ($pesterPath in $pesterPaths) {
        takeown /F $pesterPath /A /R
        icacls $pesterPath /reset
        # grant permissions to Administrators group, but use SID to do
        # it because it is localized on non-us installations of Windows
        icacls $pesterPath /grant "*S-1-5-32-544:F" /inheritance:d /T
        Remove-Item -Path $pesterPath -Recurse -Force -Confirm:$false
    }
}

Uninstall-Pester

@jasonrush good point. I spent some time and refactored into a true cmdlet using advanced function syntax. The module name is Utils and must be installed in a location located within $env:PSModulePath. The file structure is:

• Utils

  • Utils.psd1

  • Utils.psm1

  • /Public

    • Uninstall-Pester.ps1

  • /Private

The Utils.psd1

@{

ModuleVersion = "1.0.0"

GUID = "e38b14a6-0d85-4be5-869e-38ed7e270126"

Author = "Your Name Here"

CompanyName = "My Company"

Copyright = "(c) 2021 My Company All rights reserved."

RootModule = "Utils.psm1"

}

Utils.ps1 file

Get-ChildItem -Filter *.ps1 -Path "$PSScriptRoot\public","$PSScriptRoot\private" -Recurse | ForEach-Object { . $_.FullName; Write-Verbose "Loaded $_.BaseName" }
Get-ChildItem -Filter *.ps1 -Path "$PSScriptRoot\public" -Recurse | ForEach-Object { Export-ModuleMember $_.BaseName; Write-Verbose "Exported $_.BaseName" }

Uninstall-Pester.ps1 file

function Uninstall-Pester {
    [CmdletBinding()]
    [OutputType([ bool ])]
    param(
        [Parameter()]
        [switch]
        $All = $false
    )
    
    begin {
        try {
            Write-Verbose -Message "[$(( Get-Date ).TimeOfDay )][$( $MyInvocation.MyCommand )]-Begin Enter"
            $result = $true
            $pesterPath = 'WindowsPowerShell\Modules\Pester'

            if ( -not $All ) {
                $pesterPath += '\3.*'
            }

            # See if there is anything to do
            $paths = @()
            foreach ( $path in @(${env:ProgramFiles}, ${env:ProgramFiles(x86)} ) ) {
                if ( $path -and ( Test-Path -Path "$path\$pesterPath" ) ) {
                    $paths += ( Get-ChildItem -Path "$path\$pesterPath" -Directory -ErrorAction SilentlyContinue ).FullName
                }
            }

            if ( -not $paths.Count ) {
                Write-Warning "There are no Pester$( if ( -not $All ) { " 3" } ) installations in Program Files and Program Files (x86)"
                $result = $false
                return
            }
        
            $isAdmin = (New-Object Security.Principal.WindowsPrincipal([Security.Principal.WindowsIdentity]::GetCurrent())).IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)
            $is32BitProcess = $pshome -like "*syswow64*"
            $is64BitOS = ( Get-WmiObject Win32_OperatingSystem ).OSArchitecture -like "64*"
            $filePath = $null
            
            switch ( $true ) {
                { ( $is32BitProcess -and -not $is64BitOS ) -or ( -not $isAdmin -and $is64BitOS ) } {
                    Write-Warning "Restarting script under 64 bit powershell as admin"
                 
                    # relaunch this script under 64 bit shell as adminstrator
                    $filePath = "$( $pshome -replace "syswow64", "System32" )\powershell.exe"
                    break
                 }
                 { -not $isAdmin } {
                     Write-Warning "Restarting script using admin privs"
                    $filePath = 'powershell.exe'
                 }
            }
            
            if ( $filePath ) {
                Start-Process -FilePath $filePath -Verb RunAs -ArgumentList "-NoLogo -NoExit -Command `" Import-Module -name Utils; Uninstall-Pester $( if( $All ) { "-All" } )  `""
                $result = $false
                return
            }
        }
        catch {
            $result = $false
            Write-Verbose -Message  "[$(( Get-Date ).TimeOfDay )][$( $MyInvocation.MyCommand )] Exception:`r`n$_"
            throw $_
        }
        finally {
            Write-Verbose -Message "[$(( Get-Date ).TimeOfDay )][$( $MyInvocation.MyCommand )]-Begin Exit"
        }
    }

    process {
        try {
            Write-Verbose -Message "[$(( Get-Date ).TimeOfDay )][$( $MyInvocation.MyCommand )]-Process Enter"
            if ( -not $result ) {
                return
            }

            foreach ($path in $paths) {
                takeown /F $path /A /R
                icacls $path /reset
                # grant permissions to Administrators group, but use SID to do
                # it because it is localized on non-us installations of Windows
                icacls $path /grant "*S-1-5-32-544:F" /inheritance:d /T
                Remove-Item -Path $path -Recurse -Force -Confirm:$false -ErrorAction SilentlyContinue
            }
        
        }
        catch {
            $result = $false
            Write-Verbose -Message  "[$(( Get-Date ).TimeOfDay )][$( $MyInvocation.MyCommand )] Exception:`r`n$_"
            throw $_
        }
        finally {
            Write-Verbose -Message "[$(( Get-Date ).TimeOfDay )][$( $MyInvocation.MyCommand )]-Process Exit"
        }
    }
    
    end {
        try {
            Write-Verbose -Message "[$(( Get-Date ).TimeOfDay )][$( $MyInvocation.MyCommand )]-End Enter"
            return $result
        }
        catch {
            Write-Verbose -Message  "[$(( Get-Date ).TimeOfDay )][$( $MyInvocation.MyCommand )] Exception:`r`n$_"
            throw $_
        }
        finally {
            Write-Verbose -Message "[$(( Get-Date ).TimeOfDay )][$( $MyInvocation.MyCommand )]-End Exit"
        }
    }
}

Thanks your script worked out for to uninstall the module. And installing manually the newer version.

Thanks, helped me with this problem.

It's the year 2026 and this is still needed. Thanks for figuring this out and sharing. 😊