anchor.diff:        expectFailure(parser, '');
       });
     });
  -
     group('characters', () {
       test('char()', () {
         var parser = char('a');
  
positive.code:       expectFailure(parser, '');
        expectFailure(parser, 'a');
      });
      test('not()', () {
        var parser = char('a').not('not a expected');
        expectFailure(parser, 'a', 0, 'not a expected');
  
negative.code:       expect(parser.parse('1\r12\r\n123\n1234').result,
               [1, 2, 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4]);
      });
      test('map()', () {
        var parser = digit().map((String each) {
          return each.charCodeAt(0) - '0'.charCodeAt(0);
        });
  