public void IteratorPositiveLegacyArgNN() {
   var test2 = new CodeUnderTest.IteratorSimpleContract.Test2();
   test2.Test1b("hello");
 }
 public void IteratorNegativeLegacyArgNN() {
   var test2 = new CodeUnderTest.IteratorSimpleContract.Test2();
   try
   {
     test2.Test1b(null);
   } catch (ArgumentException) {
     // An ArgumentException is thrown by the legacy precondition. 
   }
 }