Pester script to validate GPOs Scope of Management

So here’s another spin on using Pester to validate operational readiness… 😉

Group policies can be pretty tricky! Troubleshooting can be a challenge. There might be even times that you start doubting yourself. Depending on the link order of your Policies, you might not get what you expected…

Operations is dynamic, things get moved around, enabled/disabled, blocked, name it and it’s bound to happen.

How about… some way to validate your GPOs Scope of Management! Once everything is working as it should, create a validation set you can verify later on. Trust me, I’ve been there… Using Pester will definitely give you that edge…

So I improvised a little on Ashley’s McGlone’s GPO Report and made a function Get-GPOsSoM. Just be sure to save it in the same folder as Domain-GPOSoM.Tests.ps1

Author: I.C.A. Strachan
Version: 1.0
Version History: Based on Ashley McGlone's Get-GPOReport. Here's a shortlink to it:
Purpose: Get all GPOs that are linked to Domain, Sites and/or OUs
Function Get-GPOsSoM {
Import-Module GroupPolicy Verbose:$false
Import-Module ActiveDirectory Verbose:$false
#region Get a list of all GPOs
$GPOs = Get-GPO All |
Select-Object ID, Path, DisplayName, GPOStatus, WMIFilter
#Array for GPLinks results
$gPLinks = @()
#region GPO Linked to the Domain
$domainGPO = @{
Identity = ((Get-ADDomain).distinguishedName)
Properties = @('name', 'distinguishedName', 'gPLink', 'gPOptions', 'canonicalname')
$gPlinks += Get-ADObject @domainGPO |
Select-Object 'name', 'distinguishedName', 'gPLink', 'gPOptions', 'canonicalname',
#region GPO Linked to OUs
$ouGPOs = @{
Filter = '*'
Properties = @('name', 'distinguishedName', 'gPLink', 'gPOptions', 'canonicalname')
$gPLinks += Get-ADOrganizationalUnit @ouGPOs |
Select-Object name, distinguishedName, gPLink, gPOptions ,canonicalname ,
@{name='Depth';expression={($_.distinguishedName -split 'OU=').count 1}}
#region GPOs linked to sites
$siteGPOs = @{
LDAPFilter = '(objectClass=site)'
SearchBase = "CN=Sites,$((Get-ADRootDSE).configurationNamingContext)"
SearchScope = 'Onelevel'
Properties = @('name', 'distinguishedName', 'gPLink', 'gPOptions', 'canonicalname')
$gPLinks += Get-ADObject @siteGPOs |
Select-Object name, distinguishedName, gPLink, gPOptions ,canonicalname,
#Hashtable to lookup GPOs
$lookupGPO = $GPOs | Group-Object AsHashTable Property 'Path'
#Get the Scope of Management of each gPLink
ForEach ($SOM in $gPLinks) {
if ($SOM.gPLink) {
If ($SOM.gPLink.length -gt 1) {
$links = @($SOM.gPLink -split {$_ -eq '[' -or $_ -eq ']'} | Where-Object {$_})
For ( $i = $links.count 1 ; $i -ge 0 ; $i ) {
$GPOData = $links[$i] -split {$_ -eq '/' -or $_ -eq ';'}
Depth = $SOM.Depth;
Name = $SOM.Name;
DistinguishedName = $SOM.distinguishedName;
canonicalName = $SOM.canonicalname;
PolicyDN = $GPOData[2];
LinkOrderNr = $links.count $i
GUID = $lookupGPO.$($GPOData[2]).ID;
DisplayName = $lookupGPO.$($GPOData[2]).DisplayName;
GPOStatus = $lookupGPO.$($GPOData[2]).GPOStatus;
WMIFilter = $lookupGPO.$($GPOData[2]).WMIFilter.Name;
Config = $GPOData[3];
LinkEnabled = [bool](!([int]$GPOData[3] -band 1));
Enforced = [bool]([int]$GPOData[3] -band 2);
BlockInheritance = [bool]($SOM.gPOptions -band 1)

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Now for the fun part! 🙂

Author: I.C.A. Strachan
Version History:
Purpose: Pester script to validate Group Polcies status and Link on Domain,Sites and OUs
Describe 'Group Policies Scope of Management validation' {
BeforeAll {
#region Get GPOs Producution Validation set
$gpoValidationSet = @'
Default Domain Policy,"DC=pshirwin,DC=local",AllSettingsEnabled,FALSE,TRUE,FALSE,1
Default Domain Controllers Policy,"OU=Domain Controllers,DC=pshirwin,DC=local",AllSettingsEnabled,FALSE,TRUE,FALSE,1
WinRM Listeners,"OU=Servers,DC=pshirwin,DC=local",AllSettingsEnabled,FALSE,TRUE,FALSE,1
'@ | ConvertFrom-Csv Delimiter ','
#Dot source Function Get-GPOsSOM.ps1
. $PSScriptRoot\Get-GPOsSOM.ps1
#Create hashtable for lookup
$lookupGPOInReport = Get-GPOsSOM | Group-Object AsHashTable Property 'DisplayName'
It 'GPOs Scope of Managment has been retrieved' {
$lookupGPOInReport | should not BeNullOrEmpty
It 'GPO validation set has been retrieved' {
$gpoValidationSet | Should not BeNullOrEmpty
foreach($set in $gpoValidationSet){
Context "GPO: $($set.DisplayName)" {
it "GPO $($set.DisplayName) exists" {
$lookupGPOInReport.$($set.DisplayName) | Should Not BeNullOrEmpty
it "GPO is linked to $($set.DistinguishedName)"{
$lookupGPOInReport.$($set.DisplayName).DistinguishedName | Should be $set.DistinguishedName
it "BlockInheritance: $($set.BlockInheritance)" {
$lookupGPOInReport.$($set.DisplayName).BlockInheritance | Should be $set.BlockInheritance
it "LinkEnabled: $($set.LinkEnabled)" {
$lookupGPOInReport.$($set.DisplayName).LinkEnabled | Should be $set.LinkEnabled
it "Group policy Enforced: $($set.Enforced)" {
$lookupGPOInReport.$($set.DisplayName).Enforced | Should be $set.Enforced
it "Group policy LinkOrder nr: $($set.LinkOrderNr)" {
$lookupGPOInReport.$($set.DisplayName).LinkOrderNr | Should be $set.LinkOrderNr
it "Group policy status: $($set.GPOStatus)" {
$lookupGPOInReport.$($set.DisplayName).GPOStatus | Should be $set.GPOStatus

So here’s the result:

Pester Test GPO SoM

Now Imagine someone changed your GPO link order:

Pester Test GPO Change Link Order

Run Pester test script again:

Pester Test GPO Change Link Order -Detected

No more doubt! The link order has been tampered with! This is definitely a game changer for Operations!

My new motto : “If you can automate it, you should test it” 😛

Pester for everyone!

Hope it’s worth something to you




2 thoughts on “Pester script to validate GPOs Scope of Management

    1. Irwin Strachan Post author

      Hi Jaap, I saw the demo scripts by Kevin Marquette and that really resonated! You can use Pester for Operations… Imagine the possibilities… 😉 Hey I’ll be seeing you next week!



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