public void ConstructorThrowsArgumentNullExceptionForNullArray()
 {
     var input = new EnumerableExpressionItemSource<char> ((char[]) null);
 }
 public void ParamsConstructorSucceedsForNonNullInput()
 {
     var input = new EnumerableExpressionItemSource<char> ("0123456789".ToCharArray ());
 }