public void ContainsKey()
        {
            TimeSpan             cacheLifeTime = TimeSpan.FromMinutes(5);
            MemoryCachingService service       = new MemoryCachingService(cacheLifeTime);
            string cachableKey = this.cachableKey;
            Foobar cachable    = GetCachableObject();

            service.Cache <Foobar>(cachableKey, cachable);
            Assert.Single(service);;
            Assert.True(service.ContainsKey(cachableKey));
        }