diff --git a/eng/common-tests/README.md b/eng/common-tests/README.md
new file mode 100644
index 00000000000..f3a29721f02
--- /dev/null
+++ b/eng/common-tests/README.md
@@ -0,0 +1,23 @@
+# About common-tests
+
+Every PowerShell source that is complex enough to have unit tests should have these tests be written in the [Pester](https://pester.dev/)
+framework and placed in `eng/common-tests/**`, i.e. this directory or one of its descendants.  
+By design, unlike `eng/common`, `eng/common-tests` is not subject to
+[mirroring to repositories](https://github.com/Azure/azure-sdk-tools/blob/main/doc/common/common_engsys.md).
+
+## When tests in this directory are executed
+
+The PowerShell Pester unit tests will be executed by the [`tools - eng-common-tests`](https://dev.azure.com/azure-sdk/internal/_build/results?buildId=220791) pipeline
+upon a PR that makes changes to `eng/common-tests/**`. The pipeline source is `eng/common-tests/ci.yml`.
+
+## How to ensure your PowerShell pester unit test is executed
+
+By Pester's default convention, the tests are to be placed in files whose
+[names ends with `.tests.ps1`](https://pester.dev/docs/usage/file-placement-and-naming),
+e.g. [`job-matrix-functions.tests.ps1`](https://github.com/Azure/azure-sdk-tools/blob/8a02e02adfc0d213509fce2764132afa74bd4ba4/eng/common-tests/matrix-generator/tests/job-matrix-functions.tests.ps1).
+
+Furthermore, each test needs to be tagged with `UnitTest`, [e.g. as seen here](https://github.com/Azure/azure-sdk-tools/blob/8a02e02adfc0d213509fce2764132afa74bd4ba4/eng/common-tests/matrix-generator/tests/job-matrix-functions.tests.ps1#L51): `Describe "Matrix-Lookup" -Tag "UnitTest", "lookup"`.
+
+Finally, as already mentioned, all such test files must be located in the path of `eng/common-tests/**`.
+
+For more, see [Invoke-Pester doc](https://pester.dev/docs/commands/Invoke-Pester).
\ No newline at end of file
diff --git a/eng/common-tests/ci.yml b/eng/common-tests/ci.yml
index 3137391791f..2375abf2c22 100644
--- a/eng/common-tests/ci.yml
+++ b/eng/common-tests/ci.yml
@@ -8,7 +8,6 @@ trigger:
       - hotfix/*
   paths:
     include:
-      - eng/common/scripts/*
       - eng/common-tests/*
 
 pr:
@@ -27,4 +26,4 @@ extends:
   template: /eng/common/pipelines/templates/stages/archetype-sdk-tool-pwsh.yml
   parameters:
     TargetDirectory: eng/common-tests/
-    TargetTags: 'UnitTest'
+    TargetTags: UnitTest
diff --git a/eng/common-tests/retrieve-codeowners.tests.ps1 b/eng/common-tests/retrieve-codeowners.tests.ps1
new file mode 100644
index 00000000000..01c805a7342
--- /dev/null
+++ b/eng/common-tests/retrieve-codeowners.tests.ps1
@@ -0,0 +1,53 @@
+Import-Module Pester
+
+BeforeAll {
+    . $PSScriptRoot/../common/scripts/get-codeowners-functions.ps1
+
+    $ToolVersion = "1.0.0-dev.20230214.3"
+    $ToolPath = (Join-Path ([System.IO.Path]::GetTempPath()) "codeowners-tool")
+    $DevOpsFeed = "https://pkgs.dev.azure.com/azure-sdk/public/_packaging/azure-sdk-for-net/nuget/v3/index.json"
+    $VsoVariable = ""
+
+    function TestGetCodeowners([string]$targetPath, [string]$codeownersFileLocation, [bool]$includeNonUserAliases = $false, [string[]]$expectedOwners) {
+      Write-Host "Test: Owners for path '$targetPath' in CODEOWNERS file at path '$codeownersFileLocation' should be '$expectedOwners'"
+      
+      $actualOwners = Get-Codeowners `
+        -ToolVersion $ToolVersion `
+        -ToolPath $ToolPath `
+        -DevOpsFeed $DevOpsFeed `
+        -VsoVariable $VsoVariable `
+        -targetPath $targetPath `
+        -codeownersFileLocation $codeownersFileLocation `
+        -includeNonUserAliases $IncludeNonUserAliases
+    
+      if ($actualOwners.Count -ne $expectedOwners.Count) {
+        Write-Error "The length of actual result is not as expected. Expected length: $($expectedOwners.Count), Actual length: $($actualOwners.Count)."
+        exit 1
+      }
+      for ($i = 0; $i -lt $expectedOwners.Count; $i++) {
+        if ($expectedOwners[$i] -ne $actualOwners[$i]) {
+          Write-Error "Expect result $expectedOwners[$i] is different than actual result $actualOwners[$i]."
+          exit 1
+        }
+      }
+    }
+}
+
+Describe "Retrieve Codeowners" -Tag "UnitTest" {
+    It "Should retrieve Codeowners" -TestCases @(
+      @{
+        codeownersPath = "$PSScriptRoot/../../.github/CODEOWNERS"; 
+        targetPath = "eng/common/scripts/get-codeowners.ps1"; 
+        expectedOwners = @("konrad-jamrozik", "weshaggard", "benbp")
+      },
+      @{
+        codeownersPath = "$PSScriptRoot/../../tools/code-owners-parser/Azure.Sdk.Tools.RetrieveCodeOwners.Tests/TestData/glob_path_CODEOWNERS"; 
+        targetPath = "tools/code-owners-parser/Azure.Sdk.Tools.RetrieveCodeOwners.Tests/TestData/InputDir/a.txt"; 
+        expectedOwners = @("2star")
+      }      
+    ) {
+      $azSdkToolsCodeowners = (Resolve-Path $codeownersPath)
+      TestGetCodeowners -targetPath $targetPath -codeownersFileLocation $azSdkToolsCodeowners -includeNonUserAliases $true -expectedOwners $expectedOwners
+      $LASTEXITCODE | Should -Be 0
+    }
+}
\ No newline at end of file
diff --git a/eng/common/pipelines/templates/stages/archetype-sdk-tool-pwsh.yml b/eng/common/pipelines/templates/stages/archetype-sdk-tool-pwsh.yml
index e01694adf03..75222cc006a 100644
--- a/eng/common/pipelines/templates/stages/archetype-sdk-tool-pwsh.yml
+++ b/eng/common/pipelines/templates/stages/archetype-sdk-tool-pwsh.yml
@@ -15,20 +15,20 @@ variables:
   - template: /eng/pipelines/templates/variables/globals.yml
 
 stages:
-  - stage: 'eng_script_tests'
+  - stage: Run_PowerShell_Tests
     jobs:
-      - job: 'Test'
+      - job: Test
         strategy:
           matrix:
             Windows:
-              Pool: 'azsdk-pool-mms-win-2022-general'
-              Image: 'windows-2022'
+              Pool: azsdk-pool-mms-win-2022-general
+              Image: windows-2022
             Linux:
               Pool: azsdk-pool-mms-ubuntu-2204-general
               Image: MMSUbuntu22.04
             Mac:
-              Pool: 'Azure Pipelines'
-              Image: 'macos-11'
+              Pool: Azure Pipelines
+              Image: macos-11
 
         pool:
           name: $(Pool)
diff --git a/eng/common/pipelines/templates/steps/run-pester-tests.yml b/eng/common/pipelines/templates/steps/run-pester-tests.yml
index 02082a6470b..ce42f65b646 100644
--- a/eng/common/pipelines/templates/steps/run-pester-tests.yml
+++ b/eng/common/pipelines/templates/steps/run-pester-tests.yml
@@ -13,7 +13,7 @@ parameters:
 
 steps:
   - pwsh: |
-     Install-Module -Name Pester -Force
+       Install-Module -Name Pester -Force
     displayName: Install Pester
 
    # default test steps
@@ -30,8 +30,10 @@ steps:
           $config.Filter.Tag = $tags
         }
 
+        Write-Host "Calling 'Invoke-Pester' in workingDirectory '$(Build.SourcesDirectory)/${{ parameters.TargetDirectory }}'. Pester tags filter: '$tags'"
+        # https://pester.dev/docs/commands/Invoke-Pester
         Invoke-Pester -Configuration $config
-      displayName: Run Tests
+      displayName: Run Pester Tests
       env: ${{ parameters.EnvVars }}
       workingDirectory: $(Build.SourcesDirectory)/${{ parameters.TargetDirectory }}
 
@@ -39,17 +41,17 @@ steps:
     - ${{ parameters.CustomTestSteps }}
 
   - task: PublishTestResults@2
-    displayName: 'Publish Test Results'
+    displayName: Publish Test Results
     condition: succeededOrFailed()
     inputs:
-      testResultsFormat: 'NUnit'
+      testResultsFormat: NUnit
       testResultsFiles: $(Build.SourcesDirectory)/${{ parameters.TargetDirectory }}/testResults.xml
-      testRunTitle: '$(System.StageName)_$(Agent.JobName)_Tests'
+      testRunTitle: $(System.StageName)_$(Agent.JobName)_Tests
 
   - task: PublishCodeCoverageResults@1
-    displayName: 'Publish Code Coverage to Azure DevOps'
+    displayName: Publish Code Coverage to Azure DevOps
     condition: succeededOrFailed()
     inputs:
-      codeCoverageTool: 'JaCoCo'
-      summaryFileLocation: '$(Build.SourcesDirectory)/${{ parameters.TargetDirectory }}/coverage.xml'
-      pathToSources: '$(Build.SourcesDirectory)/${{ parameters.TargetDirectory }}'
\ No newline at end of file
+      codeCoverageTool: JaCoCo
+      summaryFileLocation: $(Build.SourcesDirectory)/${{ parameters.TargetDirectory }}/coverage.xml
+      pathToSources: $(Build.SourcesDirectory)/${{ parameters.TargetDirectory }}
\ No newline at end of file
diff --git a/eng/common/scripts/get-codeowners-functions.ps1 b/eng/common/scripts/get-codeowners-functions.ps1
new file mode 100644
index 00000000000..ffb97173173
--- /dev/null
+++ b/eng/common/scripts/get-codeowners-functions.ps1
@@ -0,0 +1,75 @@
+function Get-CodeownersTool([string] $ToolPath, [string] $DevOpsFeed, [string] $ToolVersion)
+{
+  $codeownersToolCommand = Join-Path $ToolPath "retrieve-codeowners"
+  # Check if the retrieve-codeowners tool exists or not.
+  if (Get-Command $codeownersToolCommand -errorAction SilentlyContinue) {
+    return $codeownersToolCommand
+  }
+  if (!(Test-Path $ToolPath)) {
+    New-Item -ItemType Directory -Path $ToolPath | Out-Null
+  }
+  Write-Host "Installing the retrieve-codeowners tool under tool path: $ToolPath ..."
+
+  # Run command under tool path to avoid dotnet tool install command checking .csproj files. 
+  # This is a bug for dotnet tool command. Issue: https://github.com/dotnet/sdk/issues/9623
+  Push-Location $ToolPath
+  dotnet tool install --tool-path $ToolPath --add-source $DevOpsFeed --version $ToolVersion "Azure.Sdk.Tools.RetrieveCodeOwners" | Out-Null
+  Pop-Location
+  # Test to see if the tool properly installed.
+  if (!(Get-Command $codeownersToolCommand -errorAction SilentlyContinue)) {
+    Write-Error "The retrieve-codeowners tool is not properly installed. Please check your tool path: $ToolPath"
+    return 
+  }
+  return $codeownersToolCommand
+}
+
+function Get-Codeowners(
+  [string] $ToolPath, 
+  [string] $DevOpsFeed,
+  [string] $ToolVersion,
+  [string] $VsoVariable,
+  [string] $targetPath,
+  [string] $targetDirectory,
+  [string] $codeownersFileLocation,
+  [bool] $includeNonUserAliases = $false)
+{
+  # Backward compaitiblity: if $targetPath is not provided, fall-back to the legacy $targetDirectory
+  if ([string]::IsNullOrWhiteSpace($targetPath)) {
+    $targetPath = $targetDirectory
+  }
+  if ([string]::IsNullOrWhiteSpace($targetPath)) {
+    Write-Error "TargetPath (or TargetDirectory) parameter must be neither null nor whitespace."
+    return ,@()
+  }
+
+  $codeownersToolCommand = Get-CodeownersTool -ToolPath $ToolPath -DevOpsFeed $DevOpsFeed -ToolVersion $ToolVersion
+  Write-Host "Executing: & $codeownersToolCommand --target-path $targetPath --codeowners-file-path-or-url $codeownersFileLocation --exclude-non-user-aliases:$(!$includeNonUserAliases)"
+  $commandOutput = & $codeownersToolCommand `
+      --target-path $targetPath `
+      --codeowners-file-path-or-url $codeownersFileLocation `
+      --exclude-non-user-aliases:$(!$includeNonUserAliases) `
+      2>&1
+
+  if ($LASTEXITCODE -ne 0) {
+    Write-Host "Command $codeownersToolCommand execution failed (exit code = $LASTEXITCODE). Output string: $commandOutput"
+    return ,@()
+  } else
+  {
+    Write-Host "Command $codeownersToolCommand executed successfully (exit code = 0). Output string length: $($commandOutput.length)"
+  }
+
+# Assert: $commandOutput is a valid JSON representing:
+# - a single CodeownersEntry, if the $targetPath was a single path
+# - or a dictionary of CodeownerEntries, keyes by each path resolved from a $targetPath glob path.
+#
+# For implementation details, see Azure.Sdk.Tools.RetrieveCodeOwners.Program.Main
+
+$codeownersJson = $commandOutput | ConvertFrom-Json
+  
+  if ($VsoVariable) {
+    $codeowners = $codeownersJson.Owners -join ","
+    Write-Host "##vso[task.setvariable variable=$VsoVariable;]$codeowners"
+  }
+
+  return ,@($codeownersJson.Owners)
+}
\ No newline at end of file
diff --git a/eng/common/scripts/get-codeowners.ps1 b/eng/common/scripts/get-codeowners.ps1
index 5c2bb9b50ab..9f2d5cdf682 100644
--- a/eng/common/scripts/get-codeowners.ps1
+++ b/eng/common/scripts/get-codeowners.ps1
@@ -63,115 +63,22 @@ param (
   #    Remove the obsolete, prefix-based CODEOWNERS matcher & related tests
   #    https://github.com/Azure/azure-sdk-tools/pull/5431
   [string]$ToolVersion = "1.0.0-dev.20230214.3",
-  [string]$ToolPath = (Join-Path ([System.IO.Path]::GetTempPath()) "codeowners-tool-path"),
+  [string]$ToolPath = (Join-Path ([System.IO.Path]::GetTempPath()) "codeowners-tool"),
   [string]$DevOpsFeed = "https://pkgs.dev.azure.com/azure-sdk/public/_packaging/azure-sdk-for-net/nuget/v3/index.json",
   [string]$VsoVariable = "",
   [switch]$IncludeNonUserAliases,
   [switch]$Test
 )
 
-function Get-CodeownersTool()
-{
-  $codeownersToolCommand = Join-Path $ToolPath "retrieve-codeowners"
-  # Check if the retrieve-codeowners tool exists or not.
-  if (Get-Command $codeownersToolCommand -errorAction SilentlyContinue) {
-    return $codeownersToolCommand
-  }
-  if (!(Test-Path $ToolPath)) {
-    New-Item -ItemType Directory -Path $ToolPath | Out-Null
-  }
-  Write-Host "Installing the retrieve-codeowners tool under tool path: $ToolPath ..."
-
-  # Run command under tool path to avoid dotnet tool install command checking .csproj files. 
-  # This is a bug for dotnet tool command. Issue: https://github.com/dotnet/sdk/issues/9623
-  Push-Location $ToolPath
-  dotnet tool install --tool-path $ToolPath --add-source $DevOpsFeed --version $ToolVersion "Azure.Sdk.Tools.RetrieveCodeOwners" | Out-Null
-  Pop-Location
-  # Test to see if the tool properly installed.
-  if (!(Get-Command $codeownersToolCommand -errorAction SilentlyContinue)) {
-    Write-Error "The retrieve-codeowners tool is not properly installed. Please check your tool path: $ToolPath"
-    return 
-  }
-  return $codeownersToolCommand
-}
-
-function Get-Codeowners(
-  [string]$targetPath,
-  [string]$targetDirectory,
-  [string]$codeownersFileLocation,
-  [bool]$includeNonUserAliases = $false)
-{
-  # Backward compaitiblity: if $targetPath is not provided, fall-back to the legacy $targetDirectory
-  if ([string]::IsNullOrWhiteSpace($targetPath)) {
-    $targetPath = $targetDirectory
-  }
-  if ([string]::IsNullOrWhiteSpace($targetPath)) {
-    Write-Error "TargetPath (or TargetDirectory) parameter must be neither null nor whitespace."
-    return ,@()
-  }
-
-  $codeownersToolCommand = Get-CodeownersTool
-  Write-Host "Executing: & $codeownersToolCommand --target-path $targetPath --codeowners-file-path-or-url $codeownersFileLocation --exclude-non-user-aliases:$(!$includeNonUserAliases)"
-  $commandOutput = & $codeownersToolCommand `
-      --target-path $targetPath `
-      --codeowners-file-path-or-url $codeownersFileLocation `
-      --exclude-non-user-aliases:$(!$includeNonUserAliases) `
-      2>&1
-
-  if ($LASTEXITCODE -ne 0) {
-    Write-Host "Command $codeownersToolCommand execution failed (exit code = $LASTEXITCODE). Output string: $commandOutput"
-    return ,@()
-  } else
-  {
-    Write-Host "Command $codeownersToolCommand executed successfully (exit code = 0). Output string length: $($commandOutput.length)"
-  }
-
-# Assert: $commandOutput is a valid JSON representing:
-# - a single CodeownersEntry, if the $targetPath was a single path
-# - or a dictionary of CodeownerEntries, keyes by each path resolved from a $targetPath glob path.
-#
-# For implementation details, see Azure.Sdk.Tools.RetrieveCodeOwners.Program.Main
-
-$codeownersJson = $commandOutput | ConvertFrom-Json
-  
-  if ($VsoVariable) {
-    $codeowners = $codeownersJson.Owners -join ","
-    Write-Host "##vso[task.setvariable variable=$VsoVariable;]$codeowners"
-  }
-
-  return ,@($codeownersJson.Owners)
-}
-
-function TestGetCodeowners([string]$targetPath, [string]$codeownersFileLocation, [bool]$includeNonUserAliases = $false, [string[]]$expectReturn) {
-  Write-Host "Test: find owners matching '$targetPath' ..."
-  
-  $actualReturn = Get-Codeowners -targetPath $targetPath -codeownersFileLocation $codeownersFileLocation -includeNonUserAliases $IncludeNonUserAliases
-
-  if ($actualReturn.Count -ne $expectReturn.Count) {
-    Write-Error "The length of actual result is not as expected. Expected length: $($expectReturn.Count), Actual length: $($actualReturn.Count)."
-    exit 1
-  }
-  for ($i = 0; $i -lt $expectReturn.Count; $i++) {
-    if ($expectReturn[$i] -ne $actualReturn[$i]) {
-      Write-Error "Expect result $expectReturn[$i] is different than actual result $actualReturn[$i]."
-      exit 1
-    }
-  }
-}
-
-if ($Test) {
-  # Most of tests here have been removed; now instead we should run tests from RetrieveCodeOwnersProgramTests, and in a way as explained in:
-  # https://github.com/Azure/azure-sdk-tools/issues/5434
-  # https://github.com/Azure/azure-sdk-tools/pull/5103#discussion_r1068680818
-  Write-Host "Running reduced test suite at `$PSScriptRoot of $PSSCriptRoot. Please see https://github.com/Azure/azure-sdk-tools/issues/5434 for more."
-
-  $azSdkToolsCodeowners = (Resolve-Path "$PSScriptRoot/../../../.github/CODEOWNERS")
-  TestGetCodeowners -targetPath "eng/common/scripts/get-codeowners.ps1" -codeownersFileLocation $azSdkToolsCodeowners -includeNonUserAliases $true -expectReturn @("konrad-jamrozik", "weshaggard", "benbp")
-  
-  $testCodeowners = (Resolve-Path "$PSScriptRoot/../../../tools/code-owners-parser/Azure.Sdk.Tools.RetrieveCodeOwners.Tests/TestData/glob_path_CODEOWNERS")
-  TestGetCodeowners -targetPath "tools/code-owners-parser/Azure.Sdk.Tools.RetrieveCodeOwners.Tests/TestData/InputDir/a.txt" -codeownersFileLocation $testCodeowners -includeNonUserAliases $true -expectReturn @("2star")
-  exit 0
-}
-else {
-  return Get-Codeowners -targetPath $TargetPath -targetDirectory $TargetDirectory -codeownersFileLocation $CodeOwnerFileLocation -includeNonUserAliases $IncludeNonUserAliases
-}
+. $PSScriptRoot/get-codeowners-functions.ps1
+
+return Get-Codeowners `
+  -ToolVersion $ToolVersion `
+  -ToolPath $ToolPath `
+  -DevOpsFeed $DevOpsFeed `
+  -VsoVariable $VsoVariable `
+  -targetPath $TargetPath `
+  -targetDirectory $TargetDirectory `
+  -codeownersFileLocation $CodeOwnerFileLocation `
+  -includeNonUserAliases $IncludeNonUserAliases
+