anchor.diff:            expect(() => plenty.add('a'), throwsUnsupportedError);
             expect(() => plenty.remove('a'), throwsUnsupportedError);
           });
  +        test('sublist', () {
  +          expect(plenty.sublist(5).toString(), plenty.toString().substring(5));
  +          expect(plenty.sublist(5, 7).toString(), plenty.toString().substring(5, 7));
  +        });
         });
         group('mutable', () {
           var empty = mutableString('');
  
positive.code:           expect(() => plenty[-1] = 'a', throwsRangeError);
            expect(() => plenty[9] = 'a', throwsRangeError);
          });
          test('adding', () {
            var mutable = mutableString('abc');
            mutable.add('d');
  
negative.code:           expect(empty.toString(), '');
            expect(plenty.toString(), 'More Dart');
          });
          test('sublist', () {
            expect(plenty.sublist(5).toString(), plenty.toString().substring(5));
            expect(plenty.sublist(5, 7).toString(), plenty.toString().substring(5, 7));
          });
        });
      });
    });
  