Add more test cases (#11)

WoofWare.PawPrint.Test/TestHarness.fs

@@ -15,3 +15,9 @@ type RunResult =
         /// Final interpreter state after we stopped executing.
         FinalState : IlMachineState
     }
+
+type TestCase =
+    {
+        FileName : string
+        ExpectedReturnCode : int
+    }