Add Pester tests for Windows Features (#1225)

* Add Windows Features Pester tests

* Move win feature tests to separate file

* Remove validation script for disc space

* Remove Windows updates test

images/win/scripts/Tests/WindowsFeatures.Tests.ps1

@@ -0,0 +1,41 @@
+Describe "WindowsFeatures" {
+
+    $testCases = @(
+        @{ FeatureName = "NET-Framework-Features" }
+        @{ FeatureName = "NET-Framework-45-Features" }
+        @{ FeatureName = "FS-iSCSITarget-Server" }
+    )
+
+    if (Test-isWin16) {
+        $testCases += @{ FeatureName = "BITS" }
+        $testCases += @{ FeatureName = "DSC-Service" }
+    }
+    if (Test-isWin19) {
+        $testCases += @{ FeatureName = "Microsoft-Windows-Subsystem-Linux" }
+    }
+
+    It "Windows Feature <FeatureName> is installed" -TestCases $testCases {
+        (Get-WindowsFeature -Name $FeatureName).InstallState | Should -Be "Installed"
+    }
+
+    if (Test-isWin19) {
+        it "Check WSL is on path" {
+            (Get-Command -Name 'wsl') | Should -BeTrue
+        }
+    }
+}
+
+Describe "ContainersFeature" {
+    It "Windows containers feature is installed" {
+        (Get-WindowsFeature -Name "Containers").InstallState | Should -Be "Installed"
+    }
+}
+
+Describe "DiskSpace" {
+    it "The image has enough disk space"{
+        $availableSpaceMB =  [math]::Round((Get-PSDrive -Name C).Free / 1MB)
+        $minimumFreeSpaceMB = 18 * 1024
+
+        $availableSpaceMB | Should -BeGreaterThan $minimumFreeSpaceMB
+    }
+}