Reorganize tests

- Pester source code moved to `test/Pester`, deleted `ext-src`.
- Pester tests (.ps1 files) moved to `test/powershell`
- xUnit tests (.cs files) moved to `test/csharp`
- Third-party script test moved to `test/shebang`

test/powershell/Measure-Command.Tests.ps1

@@ -0,0 +1,28 @@
+$here = Split-Path -Parent $MyInvocation.MyCommand.Path
+
+Describe "Measure-Command" {
+
+    Context "Validate return types for Measure-Command" {
+
+        It "Should return TimeSpan as the return type" {
+            (Measure-Command { Get-Date }).GetType() | Should Be timespan
+        }
+    }
+
+    Context "Validate that it is executing commands correctly" {
+
+        It "Should return TimeSpan after executing a script" {
+            (Measure-Command { echo hi }).GetType() | Should Be timespan
+        }
+
+        It "Should return TimeSpan after executing a cmdlet" {
+            $pesterscript = "$here/assets/echoscript.ps1"
+            $testfile = "$here/assets/echoscript.ps1"
+            $testcommand = "echo pestertestscript"
+            $testcommand | Add-Content -Path $testfile
+
+            (Measure-Command { $pesterscript }).GetType() | Should Be timespan
+            Remove-Item $testfile
+        }
+    }
+}