public void TestEnumerators()
        {
            TimeSpan             cacheLifeTime = TimeSpan.FromMinutes(5);
            MemoryCachingService service       = new MemoryCachingService(cacheLifeTime);
            Foobar cachable = GetCachableObject();

            string cachableKey = this.cachableKey;

            service.Cache(cachableKey, cachable);

            IEnumerator <KeyValuePair <string, ICachedObjectBasic> > typedEnumerator
                = service.GetEnumerator();
            IEnumerator enumerator = ((IEnumerable)service).GetEnumerator();

            typedEnumerator.MoveNext();
            enumerator.MoveNext();
            Assert.Equal(cachable,
                         (Foobar)((ICachedObjectBasic)(typedEnumerator.Current).Value).UntypedValue);
            Assert.Equal(cachable,
                         (Foobar)((ICachedObjectBasic)((KeyValuePair <string, ICachedObjectBasic>)
                                                           (enumerator.Current)).Value).UntypedValue);
        }