anchor.diff:  
       group('constructors', () {
         test('missing loader', () {
  -        expect(() => new Cache.expiry(accessExpiry: new Duration(seconds: 20)),
  -            throwsArgumentError);
  +        expect(
  +            () => new Cache.expiry(accessExpiry: const Duration(seconds: 20)), throwsArgumentError);
         });
         test('missing expiry', () {
           expect(() => new Cache.expiry(loader: immediateLoader), throwsArgumentError);
         });
         test('negative access expiry', () {
  -        expect(() => new Cache.expiry(loader: immediateLoader, accessExpiry: Duration.ZERO), throwsArgumentError);
  +        expect(() => new Cache.expiry(loader: immediateLoader, accessExpiry: Duration.ZERO),
  +            throwsArgumentError);
         });
         test('negative update expiry', () {
  -        expect(() => new Cache.expiry(loader: immediateLoader, updateExpiry: Duration.ZERO), throwsArgumentError);
  +        expect(() => new Cache.expiry(loader: immediateLoader, updateExpiry: Duration.ZERO),
  +            throwsArgumentError);
         });
       });
   
  
positive.code:             .get(0)
              .then((value) => expect(value, '0', reason: 'value is loaded'))
              .then((value) => expect(counter, 1, reason: 'loaded once'))
              .then((_) => offset = new Duration(seconds: 20))
              .then((_) => cache.get(0))
              .then((value) => expect(value, '0', reason: 'value is still present'))
              .then((value) => expect(counter, 1, reason: 'still loaded once'))
              .then((_) => offset = new Duration(seconds: 21))
              .then((_) => cache.get(0))
              .then((value) => expect(value, '0', reason: 'value is reloaded'))
              .then((value) => expect(counter, 2, reason: 'value loaded again'));
  
negative.code:         var cache = newUpdateExpireCache(immediateLoader);
          return cache
              .set(1, '2')
              .then((_) => offset = const Duration(seconds: 20))
              .then((_) => cache.getIfPresent(1))
              .then((value) => expect(value, '2', reason: 'value is set'))
              .then((_) => cache.set(1, '3'))
              .then((_) => offset = const Duration(seconds: 40))
              .then((_) => cache.getIfPresent(1))
              .then((value) => expect(value, '3', reason: 'value is updated'))
              .then((_) => offset = const Duration(seconds: 41))
              .then((_) => cache.getIfPresent(1))
              .then((value) => expect(value, isNull, reason: 'value has expried'));
        });
  