anchor.diff:      });
       test('failure', () {
         final lines = <String>[];
  -      expect(trace(identifier, lines.add).parse('1').isFailure,
  -          isTrue);
  +      expect(trace(identifier, lines.add).parse('1').isFailure, isTrue);
         expect(lines, [
           'Instance of \'SequenceParser\'',
           '  Instance of \'CharacterParser\'[letter expected]',
  
positive.code:   group('trace', () {
      test('success', () {
        final lines = <String>[];
        expect(trace(identifier, lines.add).parse('a').isSuccess,
            isTrue);
        expect(lines, [
          'Instance of \'SequenceParser\'',
          '  Instance of \'CharacterParser\'[letter expected]',
  
negative.code:     });
      test('failure', () {
        final lines = <String>[];
        expect(progress(identifier, lines.add).parse('1').isFailure, isTrue);
        expect(lines, [
          '* Instance of \'SequenceParser\'',
          '* Instance of \'CharacterParser\'[letter expected]'
  