diff --git a/Examples/Example-16-AddRemoveGPOPermission01.ps1 b/Examples/Example-16-AddRemoveGPOPermission01.ps1
index 0e8c6d9..83884f0 100644
--- a/Examples/Example-16-AddRemoveGPOPermission01.ps1
+++ b/Examples/Example-16-AddRemoveGPOPermission01.ps1
@@ -1,21 +1,23 @@
 Import-Module "$PSScriptRoot\..\GPoZaurr.psd1" -Force
 
-#$T = Get-GPOZaurrPermission -GPOName 'ALL | Enable RDP' #-IncludeGPOObject #-ExcludePermissionType GpoApply,GpoRead -IncludeGPOObject
-#$T | Format-Table -AutoSize *
+$T = Get-GPOZaurrPermission -GPOName 'ALL | Enable RDP' #-IncludeGPOObject #-ExcludePermissionType GpoApply,GpoRead -IncludeGPOObject
+$T | Format-Table -AutoSize *
 
 #Add-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'CN=Przemysław Kłys,OU=Users,OU=Accounts,OU=Production,DC=ad,DC=evotec,DC=xyz' -PrincipalType DistinguishedName -Verbose #-WhatIf
-#Add-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name -Verbose #-WhatIf
-#Add-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'S-1-5-21-853615985-2870445339-3163598659-1105' -PrincipalType Sid -Verbose #-WhatIf
+#Add-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'CN=Administrator,OU=Special,OU=Accounts,OU=Production,DC=ad,DC=evotec,DC=xyz' -PrincipalType DistinguishedName -Verbose #-WhatIf
 
-#$T = Get-GPOZaurrPermission -GPOName 'ALL | Enable RDP' #-ExcludePermissionType GpoApply,GpoRead -IncludeGPOObject
-#$T | Format-Table -AutoSize *
+Add-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name -Verbose #-WhatIf
+Add-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'S-1-5-21-853615985-2870445339-3163598659-1105' -PrincipalType Sid -Verbose #-WhatIf
+
+$T = Get-GPOZaurrPermission -GPOName 'ALL | Enable RDP' #-ExcludePermissionType GpoApply,GpoRead -IncludeGPOObject
+$T | Format-Table -AutoSize *
 
 Add-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEditDeleteModifySecurity -Principal 'Domain Admins' -PrincipalType Name -Verbose #-WhatIf
-#Remove-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name -Verbose #-WhatIf
-#Remove-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'EVOTEC\przemyslaw.klys' -PrincipalType NetbiosName -Verbose #-WhatIf
-#Remove-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'CN=Przemysław Kłys,OU=Users,OU=Accounts,OU=Production,DC=ad,DC=evotec,DC=xyz' -PrincipalType DistinguishedName -Verbose #-WhatIf
-#Remove-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Type NotAdministrative -Verbose
+Remove-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name -Verbose #-WhatIf
+Remove-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'EVOTEC\przemyslaw.klys' -PrincipalType NetbiosName -Verbose #-WhatIf
+Remove-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Principal 'CN=Przemysław Kłys,OU=Users,OU=Accounts,OU=Production,DC=ad,DC=evotec,DC=xyz' -PrincipalType DistinguishedName -Verbose #-WhatIf
+Remove-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEdit -Type NotAdministrative -Verbose
 
 Remove-GPOZaurrPermission -GPOName 'ALL | Enable RDP' -PermissionType GpoEditDeleteModifySecurity -PrincipalType DistinguishedName -Principal 'CN=Domain Admins,CN=Users,DC=ad,DC=evotec,DC=pl' -Verbose
-#$T = Get-GPOZaurrPermission -GPOName 'ALL | Enable RDP' #-ExcludePermissionType GpoApply,GpoRead -IncludeGPOObject
-#$T | Format-Table -AutoSize *
\ No newline at end of file
+$T = Get-GPOZaurrPermission -GPOName 'ALL | Enable RDP' #-ExcludePermissionType GpoApply,GpoRead -IncludeGPOObject
+$T | Format-Table -AutoSize *
\ No newline at end of file
diff --git a/GPOZaurr.Tests.ps1 b/GPOZaurr.Tests.ps1
new file mode 100644
index 0000000..f0e735a
--- /dev/null
+++ b/GPOZaurr.Tests.ps1
@@ -0,0 +1,59 @@
+$ModuleName = (Get-ChildItem $PSScriptRoot\*.psd1).BaseName
+$PrimaryModule = Get-ChildItem -Path $PSScriptRoot -Filter '*.psd1' -Recurse -ErrorAction SilentlyContinue -Depth 1
+if (-not $PrimaryModule) {
+    throw "Path $PSScriptRoot doesn't contain PSD1 files. Failing tests."
+}
+if ($PrimaryModule.Count -ne 1) {
+    throw 'More than one PSD1 files detected. Failing tests.'
+}
+$PSDInformation = Import-PowerShellDataFile -Path $PrimaryModule.FullName
+$RequiredModules = @(
+    'Pester'
+    'PSWriteColor'
+    'PSParseHTML'
+    if ($PSDInformation.RequiredModules) {
+        $PSDInformation.RequiredModules
+    }
+)
+foreach ($Module in $RequiredModules) {
+    if ($Module -is [System.Collections.IDictionary]) {
+        $Exists = Get-Module -ListAvailable -Name $Module.ModuleName
+        if (-not $Exists) {
+            Write-Warning "$ModuleName - Downloading $($Module.ModuleName) from PSGallery"
+            Install-Module -Name $Module.ModuleName -Force -SkipPublisherCheck
+        }
+    } else {
+        $Exists = Get-Module -ListAvailable $Module -ErrorAction SilentlyContinue
+        if (-not $Exists) {
+            Install-Module -Name $Module -Force -SkipPublisherCheck
+        }
+    }
+}
+
+Write-Color 'ModuleName: ', $ModuleName, ' Version: ', $PSDInformation.ModuleVersion -Color Yellow, Green, Yellow, Green -LinesBefore 2
+Write-Color 'PowerShell Version: ', $PSVersionTable.PSVersion -Color Yellow, Green
+Write-Color 'PowerShell Edition: ', $PSVersionTable.PSEdition -Color Yellow, Green
+Write-Color 'Required modules: ' -Color Yellow
+foreach ($Module in $PSDInformation.RequiredModules) {
+    if ($Module -is [System.Collections.IDictionary]) {
+        Write-Color '   [>] ', $Module.ModuleName, ' Version: ', $Module.ModuleVersion -Color Yellow, Green, Yellow, Green
+    } else {
+        Write-Color '   [>] ', $Module -Color Yellow, Green
+    }
+}
+Write-Color
+
+Import-Module $PSScriptRoot\*.psd1 -Force
+Import-Module Pester -Force
+$Configuration = [PesterConfiguration]::Default
+$Configuration.Run.Path = "$PSScriptRoot\Tests"
+$Configuration.Run.Exit = $true
+$Configuration.Should.ErrorAction = 'Continue'
+$Configuration.CodeCoverage.Enabled = $false
+$Configuration.Output.Verbosity = 'Detailed'
+$Result = Invoke-Pester -Configuration $Configuration
+#$result = Invoke-Pester -Script $PSScriptRoot\Tests -Verbose -Output Detailed #-EnableExit
+
+if ($Result.FailedCount -gt 0) {
+    throw "$($Result.FailedCount) tests failed."
+}
\ No newline at end of file
diff --git a/Public/Add-GPOZaurrPermission.ps1 b/Public/Add-GPOZaurrPermission.ps1
index 8724ecb..1ffb63c 100644
--- a/Public/Add-GPOZaurrPermission.ps1
+++ b/Public/Add-GPOZaurrPermission.ps1
@@ -153,6 +153,13 @@
                         if ($Type -eq 'Default') {
                             Write-Verbose "Add-GPOZaurrPermission - Adding permission $PermissionType for $($Principal) to $($GPO.DisplayName) at $($GPO.DomainName)"
                             $CountFixed++
+                            if ($PrincipalType -eq 'DistinguishedName') {
+                                $ADIdentity = Get-WinADObject -Identity $Principal
+                                if ($ADIdentity) {
+                                    Write-Verbose "Add-GPOZaurrPermission - Need to convert DN $Principal to SID $($ADIdentity.ObjectSID) to $($GPO.DisplayName) at $($GPO.DomainName)"
+                                    $Principal = $ADIdentity.ObjectSID
+                                }
+                            }
                             if ($PSCmdlet.ShouldProcess($GPO.DisplayName, "Adding $Principal / $PermissionType to $($GPO.DisplayName) at $($GPO.DomainName)")) {
                                 try {
                                     Write-Verbose "Add-GPOZaurrPermission - Adding permission $PermissionType for $($Principal)"
diff --git a/Tests/GetAddRemoveGPOPermissions.Tests.ps1 b/Tests/GetAddRemoveGPOPermissions.Tests.ps1
new file mode 100644
index 0000000..41fb159
--- /dev/null
+++ b/Tests/GetAddRemoveGPOPermissions.Tests.ps1
@@ -0,0 +1,69 @@
+Describe 'GPO Permissions Management - Simple' {
+    BeforeAll {
+        # just in case some tests failed before and added user stays
+        Remove-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -PermissionType GpoEdit -Principal 'EVOTEC\przemyslaw.klys' -PrincipalType NetbiosName -Verbose
+    }
+    It 'Get-GPOZaurrPermission - Should return proper data' {
+        $GPOPermissions = Get-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing'
+        ($GPOPermissions | Where-Object { $_.Permission -eq 'GPOApply' }) | Should -BeOfType PSCustomObject
+        ($GPOPermissions | Where-Object { $_.Permission -eq 'GPOApply' }).PrincipalNetBiosName | Should -Be 'NT AUTHORITY\Authenticated Users'
+
+        $GPOPermissions = Get-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -IncludePermissionType GpoEditDeleteModifySecurity -Type NotAdministrative
+        $GPOPermissions.PrincipalNetBiosName | Should -Be 'NT AUTHORITY\SYSTEM'
+        $GPOPermissions.PrincipalSidType | Should -Be 'WellKnownAdministrative'
+        $GPOPermissions.PrincipalObjectClass | Should -Be 'foreignSecurityPrincipal'
+        $GPOPermissions.DisplayName | Should -be 'TEST | GPOZaurr Permissions Testing'
+        $GPOPermissions.Permission | Should -Be 'GpoEditDeleteModifySecurity'
+
+        [Array] $GPOPermissions = Get-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -IncludePermissionType GpoEditDeleteModifySecurity
+        $GPOPermissions.Count | Should -be 3
+        $SYSTEM = $GPOPermissions | Where-Object { $_.PrincipalNetBiosName -eq 'NT AUTHORITY\SYSTEM' }
+        $SYSTEM.PrincipalNetBiosName | Should -Be 'NT AUTHORITY\SYSTEM'
+        $SYSTEM.PrincipalSidType | Should -Be 'WellKnownAdministrative'
+        $SYSTEM.PrincipalObjectClass | Should -Be 'foreignSecurityPrincipal'
+        $SYSTEM.DisplayName | Should -be 'TEST | GPOZaurr Permissions Testing'
+        $SYSTEM.Permission | Should -Be 'GpoEditDeleteModifySecurity'
+
+        $DomainAdmins = $GPOPermissions | Where-Object { $_.PrincipalNetBiosName -eq 'EVOTEC\Domain Admins' }
+        $DomainAdmins.PrincipalNetBiosName | Should -Be 'EVOTEC\Domain Admins'
+        $DomainAdmins.PrincipalSidType | Should -Be 'Administrative'
+        $DomainAdmins.PrincipalObjectClass | Should -Be 'group'
+        $DomainAdmins.DisplayName | Should -be 'TEST | GPOZaurr Permissions Testing'
+        $DomainAdmins.Permission | Should -Be 'GpoEditDeleteModifySecurity'
+
+        $EnterpriseAdmins = $GPOPermissions | Where-Object { $_.PrincipalNetBiosName -eq 'EVOTEC\Enterprise Admins' }
+        $EnterpriseAdmins.PrincipalNetBiosName | Should -Be 'EVOTEC\Enterprise Admins'
+        $EnterpriseAdmins.PrincipalSidType | Should -Be 'Administrative'
+        $EnterpriseAdmins.PrincipalObjectClass | Should -Be 'group'
+        $EnterpriseAdmins.DisplayName | Should -be 'TEST | GPOZaurr Permissions Testing'
+        $EnterpriseAdmins.Permission | Should -Be 'GpoEditDeleteModifySecurity'
+    }
+    It 'Add-GPOZaurrPermission - With WHATIF works' {
+        # Tests WHATIF
+        Add-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -PermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name -Verbose -WhatIf
+
+        $GPOPermissions = Get-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -IncludePermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name
+        $GPOPermissions | Should -be $null
+    }
+    It 'Add-GPOZaurrPermission - Without WHATIF works' {
+        Add-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -PermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name -Verbose
+
+        $GPOPermissions = Get-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -IncludePermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name
+        $GPOPermissions | Should -be -Not $null
+        $GPOPermissions.PrincipalNetBiosName | Should -Be 'EVOTEC\przemyslaw.klys'
+    }
+    It 'Remove-GPOZaurrPermission - With WHATIF' {
+        # Tests WHATIF
+        Remove-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -PermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name -Verbose -WhatIf
+
+        $GPOPermissions = Get-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -IncludePermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name
+        $GPOPermissions | Should -be -Not $null
+        $GPOPermissions.PrincipalNetBiosName | Should -Be 'EVOTEC\przemyslaw.klys'
+
+    }
+    It 'Remove-GPOZaurrPermission - Without WHATIF' {
+        Remove-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -PermissionType GpoEdit -Principal 'EVOTEC\przemyslaw.klys' -PrincipalType NetbiosName -Verbose
+        $GPOPermissions = Get-GPOZaurrPermission -GPOName 'TEST | GPOZaurr Permissions Testing' -IncludePermissionType GpoEdit -Principal 'przemyslaw.klys' -PrincipalType Name
+        $GPOPermissions | Should -be $null
+    }
+}
\ No newline at end of file