anchor.diff:            expect(diff['action'], equals('change'));
             expect(diff['_id'], equals('january'));
             Map strippedData = _stripPrivateFields(diff['data']);
  -          expect(strippedData, equals(february));
  +          expect(strippedData, equals(january2));
             expect(diff['author'], equals('Michael Smith'));
           });
       });
   
       test('change not existing data. (T05)', () {
         // when
  -      Future shouldThrow =  ready.then((_) => months.change('january', new Map.from(february), 'Michael Smith'));
  +      Future shouldThrow =  ready.then((_) => months.change('january', new Map.from(january), 'Michael Smith'));
   
         //then
           expect(shouldThrow, throws);
  
positive.code:         });
      });
  
      test('remove non-existing data. (T08)', () {
        // when
        Future shouldNotThrow =ready.then((_) => months.remove('january', 'Michael Smith'));
  
  
negative.code: 
      test('change data. (T04)', () {
        // given
        Map january2 = {'name': 'January2', 'days': 11, 'number': 4, '_id': 'january'};
        return ready.then((_) => months.add(new Map.from(january), 'John Doe'))
  
        // when
          .then((_) => months.change('january', new Map.from(january2), 'Michael Smith'))
          .then((_) => months.data())
          .then((data){
  
        // then
            expect(data['data'].length, equals(1));
            Map strippedData = _stripPrivateFields(data['data'][0]);
            expect(strippedData, equals(january2));
            expect(data['version'], equals(2));
        }).then((_) => months.diffFromVersion(1))
          .then((dataDiff) {
  