anchor.diff:  
       test('remove data. (T07)', () {
         // given
  -      Future toRemove = ready.then((_) => months.add(new Map.from(january), 'John Doe'))
  +      Future toRemove = ready.then((_) => months.add(clone(january), 'John Doe'))
   
         // when
           .then((_) => months.remove('january', 'Michael Smith'));
  
positive.code: 
      test('deprecatedChange not existing data. (T11)', () {
        // when
        Future shouldThrow =  ready.then((_) => months.deprecatedChange('january', new Map.from(january), 'Michael Smith'));
  
        //then
          expect(shouldThrow, throws);
  
negative.code: 
      test('add data. (T02)', () {
        // when
        return ready.then((_) => months.add(clone(january), 'John Doe'))
          .then((_) => months.data())
          .then((data){
  
  