Add RuleToTest parameter to Test-ScriptAnalyzer to aid with test driv…

…en rule development

build.psm1

@@ -289,7 +289,14 @@ function Start-ScriptAnalyzerBuild
 function Test-ScriptAnalyzer
 {
     [CmdletBinding()]
-    param ( [Parameter()][switch]$InProcess, [switch]$ShowAll )
+    param (
+        [Parameter()]
+        [switch]$InProcess,
+
+        [switch]$ShowAll,
+
+        [string]$RuleToTest
+    )
 
     END {
         # versions 3 and 4 don't understand versioned module paths, so we need to rename the directory of the version to
@@ -319,7 +326,12 @@ function Test-ScriptAnalyzer
             $testModulePath = Join-Path "${projectRoot}" -ChildPath out
         }
         $testResultsFile = "'$(Join-Path ${projectRoot} -childPath TestResults.xml)'"
-        $testScripts = "'${projectRoot}\Tests\Engine','${projectRoot}\Tests\Rules','${projectRoot}\Tests\Documentation'"
+        if ($RuleToTest) {
+            $testScripts = Get-Childitem -Path "${projectRoot}\Tests\Rules" -Filter *$RuleToTest*.tests.ps1 | Select-Object -ExpandProperty FullName
+        }
+        else {
+            $testScripts = "'${projectRoot}\Tests\Engine','${projectRoot}\Tests\Rules','${projectRoot}\Tests\Documentation'"
+        }
         try {
             if ( $major -lt 5 ) {
                 Rename-Item $script:destinationDir ${testModulePath}