diff --git a/eng/common/scripts/check-spelling-in-changed-files.ps1 b/eng/common/scripts/check-spelling-in-changed-files.ps1
index 55bc3d03395e..8ac20c182532 100644
--- a/eng/common/scripts/check-spelling-in-changed-files.ps1
+++ b/eng/common/scripts/check-spelling-in-changed-files.ps1
@@ -34,8 +34,16 @@ Optional location to use for cspell.json path. Default value is
 .PARAMETER ExitWithError
 Exit with error code 1 if spelling errors are detected.
 
-.PARAMETER Test
-Run test functions against the script logic
+.PARAMETER SourceCommittish
+Commit SHA (or ref) used for file list generation. This is the later commit. The
+default value is useful for Azure DevOps pipelines. The default value is
+`${env:SYSTEM_PULLREQUEST_SOURCECOMMITID}`
+
+.PARAMETER TargetCommittish
+Commit SHA (or ref) used for file list generation. This is the "base" commit.
+The default value is useful for Azure DevOps pipelines. The default value is
+`origin/${env:SYSTEM_PULLREQUEST_TARGETBRANCH}` with some string manipulation to
+remove the `refs/heads/` prefix.
 
 .EXAMPLE
 ./eng/common/scripts/check-spelling-in-changed-files.ps1 
@@ -57,199 +65,14 @@ Param (
     [switch] $ExitWithError,
 
     [Parameter()]
-    [switch] $Test
+    [string]$SourceCommittish = "${env:SYSTEM_PULLREQUEST_SOURCECOMMITID}",
+
+    [Parameter()]
+    [string]$TargetCommittish = ("origin/${env:SYSTEM_PULLREQUEST_TARGETBRANCH}" -replace "refs/heads/")
 )
 
 Set-StrictMode -Version 3.0
 
-function TestSpellChecker() {
-    Test-Exit0WhenAllFilesExcluded
-    ResetTest
-    Test-Exit1WhenIncludedFileHasSpellingError
-    ResetTest
-    Test-Exit0WhenIncludedFileHasNoSpellingError
-    ResetTest
-    Test-Exit1WhenChangedFileAlreadyHasSpellingError
-    ResetTest
-    Test-Exit0WhenUnalteredFileHasSpellingError
-    ResetTest
-    Test-Exit0WhenSpellingErrorsAndNoExitWithError
-}
-
-function Test-Exit0WhenAllFilesExcluded() {
-    # Arrange
-    "sepleing errrrrorrrrr" > ./excluded/excluded-file.txt
-    git add -A
-    git commit -m "One change"
-
-    # Act
-    &"$PSScriptRoot/check-spelling-in-changed-files.ps1" `
-        -CspellConfigPath "./.vscode/cspell.json" `
-        -SpellCheckRoot "./" `
-        -ExitWithError
-
-    # Assert
-    if ($LASTEXITCODE -ne 0) {
-        throw "`$LASTEXITCODE != 0"
-    }
-}
-
-function Test-Exit1WhenIncludedFileHasSpellingError() {
-    # Arrange
-    "sepleing errrrrorrrrr" > ./included/included-file.txt
-    git add -A
-    git commit -m "One change"
-
-    # Act
-    &"$PSScriptRoot/check-spelling-in-changed-files.ps1" `
-        -CspellConfigPath "./.vscode/cspell.json" `
-        -SpellCheckRoot "./" `
-        -ExitWithError
-
-    # Assert
-    if ($LASTEXITCODE -ne 1) {
-        throw "`$LASTEXITCODE != 1"
-    }
-}
-
-function Test-Exit0WhenIncludedFileHasNoSpellingError() {
-    # Arrange
-    "correct spelling" > ./included/included-file.txt
-    git add -A
-    git commit -m "One change"
-
-    # Act
-    &"$PSScriptRoot/check-spelling-in-changed-files.ps1" `
-        -CspellConfigPath "./.vscode/cspell.json" `
-        -SpellCheckRoot "./" `
-        -ExitWithError
-
-    # Assert
-    if ($LASTEXITCODE -ne 0) {
-        throw "`$LASTEXITCODE != 0"
-    }
-}
-
-function Test-Exit1WhenChangedFileAlreadyHasSpellingError() {
-    # Arrange
-    "sepleing errrrrorrrrr" > ./included/included-file.txt
-    git add -A
-    git commit -m "First change"
-
-    "A statement without spelling errors" >> ./included/included-file.txt
-    git add -A
-    git commit -m "Second change"
-
-    # Act
-    &"$PSScriptRoot/check-spelling-in-changed-files.ps1" `
-        -CspellConfigPath "./.vscode/cspell.json" `
-        -SpellCheckRoot "./" `
-        -ExitWithError
-
-    # Assert
-    if ($LASTEXITCODE -ne 1) {
-        throw "`$LASTEXITCODE != 1"
-    }
-}
-
-function Test-Exit0WhenUnalteredFileHasSpellingError() {
-    # Arrange
-    "sepleing errrrrorrrrr" > ./included/included-file-1.txt
-    git add -A
-    git commit -m "One change"
-
-    "A statement without spelling errors" > ./included/included-file-2.txt
-    git add -A
-    git commit -m "Second change"
-
-    # Act
-    &"$PSScriptRoot/check-spelling-in-changed-files.ps1" `
-        -CspellConfigPath "./.vscode/cspell.json" `
-        -SpellCheckRoot "./" `
-        -ExitWithError
-
-    # Assert
-    if ($LASTEXITCODE -ne 0) {
-        throw "`$LASTEXITCODE != 0"
-    }
-}
-
-function Test-Exit0WhenSpellingErrorsAndNoExitWithError() {
-    # Arrange
-    "sepleing errrrrorrrrr" > ./included/included-file-1.txt
-    git add -A
-    git commit -m "One change"
-
-    # Act
-    &"$PSScriptRoot/check-spelling-in-changed-files.ps1" `
-        -CspellConfigPath "./.vscode/cspell.json" `
-        -SpellCheckRoot "./"
-
-    # Assert
-    if ($LASTEXITCODE -ne 0) {
-        throw "`$LASTEXITCODE != 0"
-    }
-}
-
-function SetupTest($workingDirectory) {
-    Write-Host "Create test temp dir: $workingDirectory"
-    New-Item -ItemType Directory -Force -Path $workingDirectory | Out-Null
-
-    Push-Location $workingDirectory | Out-Null
-    git init
-
-    New-Item -ItemType Directory -Force -Path "./excluded"
-    New-Item -ItemType Directory -Force -Path "./included"
-    New-Item -ItemType Directory -Force -Path "./.vscode"
-
-    "Placeholder" > "./excluded/placeholder.txt"
-    "Placeholder" > "./included/placeholder.txt"
-
-    $configJsonContent = @"
-{
-    "version": "0.1",
-    "language": "en",
-    "ignorePaths": [
-        ".vscode/cspell.json",
-        "excluded/**"
-    ]
-}
-"@
-    $configJsonContent > "./.vscode/cspell.json"
-
-    git add -A
-    git commit -m "Init"
-}
-
-function ResetTest() {
-    # Empty out the working tree
-    git checkout .
-    git clean -xdf
-
-    $revCount = git rev-list --count HEAD
-    if ($revCount -gt 1) {
-        # Reset N-1 changes so there is only the initial commit
-        $revisionsToReset = $revCount - 1
-        git reset --hard HEAD~$revisionsToReset
-    }
-}
-
-function TeardownTest($workingDirectory) {
-    Pop-Location | Out-Null
-    Write-Host "Remove  test temp dir: $workingDirectory"
-    Remove-Item -Path $workingDirectory -Recurse -Force | Out-Null
-}
-
-if ($Test) {
-    $workingDirectory = Join-Path ([System.IO.Path]::GetTempPath()) ([System.IO.Path]::GetRandomFileName())
-
-    SetupTest $workingDirectory
-    TestSpellChecker
-    TeardownTest $workingDirectory
-    Write-Host "Test complete"
-    exit 0
-}
-
 $ErrorActionPreference = "Continue"
 . $PSScriptRoot/common.ps1
 
@@ -266,7 +89,9 @@ if (!(Test-Path $CspellConfigPath)) {
 # Lists names of files that were in some way changed between the
 # current branch and default target branch. Excludes files that were deleted to
 # prevent errors in Resolve-Path
-$changedFilesList = Get-ChangedFiles
+$changedFilesList = Get-ChangedFiles `
+    -SourceCommittish $SourceCommittish `
+    -TargetCommittish $TargetCommittish
 
 $changedFiles = @()
 foreach ($file in $changedFilesList) {
diff --git a/eng/common/spelling/Invoke-Cspell.ps1 b/eng/common/spelling/Invoke-Cspell.ps1
index 509c6b00effa..4e5baa0bdf33 100644
--- a/eng/common/spelling/Invoke-Cspell.ps1
+++ b/eng/common/spelling/Invoke-Cspell.ps1
@@ -27,9 +27,6 @@ If set the PackageInstallCache will not be deleted. Use if there are multiple
 calls to Invoke-Cspell.ps1 to prevent creating multiple working directories and
 redundant calls `npm ci`.
 
-.PARAMETER Test
-Run test functions against the script logic
-
 .EXAMPLE
 ./eng/common/scripts/Invoke-Cspell.ps1 -ScanGlobs 'sdk/*/*/PublicAPI/**/*.md'
 
@@ -64,10 +61,7 @@ param(
   [string] $PackageInstallCache = (Join-Path ([System.IO.Path]::GetTempPath()) "cspell-tool-path"),
 
   [Parameter()]
-  [switch] $LeavePackageInstallCache,
-
-  [Parameter()]
-  [switch] $Test
+  [switch] $LeavePackageInstallCache
 )
 
 Set-StrictMode -Version 3.0
@@ -82,30 +76,6 @@ if (!(Test-Path $CSpellConfigPath)) {
   exit 1
 }
 
-function Test-VersionReportMatches() {
-  # Arrange
-  $expectedPackageVersion = '6.12.0'
-
-  # Act
-  $actual = &"$PSScriptRoot/Invoke-Cspell.ps1" `
-    -JobType '--version'
-
-  # Assert
-  if ($actual -ne $expectedPackageVersion) {
-    throw "Mismatched version. Expected:`n$expectedPackageVersion`n`nActual:`n$actual"
-  }
-}
-
-function TestInvokeCspell() {
-  Test-VersionReportMatches
-}
-
-if ($Test) {
-  TestInvokeCspell
-  Write-Host "Test complete"
-  exit 0
-}
-
 # Prepare the working directory if it does not already have requirements in
 # place.
 if (!(Test-Path $PackageInstallCache)) {
@@ -170,10 +140,11 @@ try {
   npm ci | Write-Host
 
   # Use the mutated configuration file when calling cspell
-  $command = "npx cspell $JobType --config $CSpellConfigPath --no-must-find-files --root $SpellCheckRoot --relative"
+  $command = "npm exec --no -- cspell $JobType --config $CSpellConfigPath --no-must-find-files --root $SpellCheckRoot --relative"
   Write-Host $command
-  $cspellOutput = npx  `
-    --no-install `
+  $cspellOutput = npm exec  `
+    --no `
+    -- `
     cspell `
     $JobType `
     --config $CSpellConfigPath `