Add comprehensive test suite, fix minor issues, rename function and file names to match approved verbs (#708)

Scripts/Features/Windows-OptionalFeatures.ps1

@@ -0,0 +1,61 @@
+# Enables a Windows optional feature and pipes its output to the console
+function Enable-WindowsFeature {
+    param (
+        [string]$FeatureName
+    )
+
+    if ($script:Params.ContainsKey("WhatIf")) {
+        Write-Host "[WhatIf] Enable Windows feature: $FeatureName" -ForegroundColor Cyan
+        Write-Host ""
+        return
+    }
+
+    $result = Invoke-NonBlocking -ScriptBlock {
+        param($name)
+        Enable-WindowsOptionalFeature -Online -FeatureName $name -All -NoRestart
+    } -ArgumentList $FeatureName
+
+    $dismResult = @($result) | Where-Object { $_ -is [Microsoft.Dism.Commands.ImageObject] }
+    if ($dismResult) {
+        Write-Host ($dismResult | Out-String).Trim()
+    }
+}
+
+# Disables a Windows optional feature and pipes its output to the console
+function Disable-WindowsFeature {
+    param (
+        [string]$FeatureName
+    )
+
+    if ($script:Params.ContainsKey("WhatIf")) {
+        Write-Host "[WhatIf] Disable Windows feature: $FeatureName" -ForegroundColor Cyan
+        Write-Host ""
+        return
+    }
+
+    $result = Invoke-NonBlocking -ScriptBlock {
+        param($name)
+        Disable-WindowsOptionalFeature -Online -FeatureName $name -NoRestart
+    } -ArgumentList $FeatureName
+
+    $dismResult = @($result) | Where-Object { $_ -is [Microsoft.Dism.Commands.ImageObject] }
+    if ($dismResult) {
+        Write-Host ($dismResult | Out-String).Trim()
+    }
+}
+
+function Test-WindowsOptionalFeatureEnabled {
+    param (
+        [Parameter(Mandatory)]
+        [string]$FeatureName
+    )
+
+    try {
+        $feature = Get-WindowsOptionalFeature -Online -FeatureName $FeatureName -ErrorAction Stop
+    }
+    catch {
+        return $false
+    }
+
+    return ($feature.State -eq 'Enabled')
+}