added Out-String tests

src/pester-tests/Out-String.Tests.ps1

@@ -0,0 +1,44 @@
+Describe "Out-String" {
+    if (Test-Path /tmp)
+    {
+        $nl = "`n"
+    }
+    else
+    {
+        $nl = "`r`n"
+    }
+
+    It "Should accumulate the strings and returns them as a single string" {
+        $testArray = "a", " b"
+        
+        $testArray.GetType().BaseType | Should Be array
+        
+        $testArray | Out-String | Should Be "a$nl b$nl"
+
+        $($testArray | Out-String).GetType() | Should Be string
+    }
+
+    It "Should be able to return an array of strings using the stream switch" {
+        $testInput = "a", "b"
+
+        $($testInput | Out-String).GetType() | Should Be string
+
+        $($testInput | Out-String -Stream).GetType().BaseType.Name | Should Be array
+    }
+
+    It "Should send all objects through a pipeline when not using the stream switch" {
+        $testInput = "a", "b"
+        $streamoutputlength = $($testInput | Out-String -Stream).Length
+        $nonstreamoutputlength = $($testInput | Out-String).Length
+
+        $nonstreamoutputlength| Should BeGreaterThan $streamoutputlength
+    }
+
+    It "Should send a single object through a pipeline when the stream switch is used" {
+        $testInput = "a", "b"
+        $streamoutputlength = $($testInput | Out-String -Stream).Length
+        $nonstreamoutputlength = $($testInput | Out-String).Length
+
+        $streamoutputlength | Should BeLessThan $nonstreamoutputlength
+    }
+}