public void ExpiringDictionary_RefreshAll_Refreshes_All_Items()
        {
            using (var map = new ExpiringDictionary <int, string>(10, 10)) {
                map.Add(22, "1");
                map.Add(23, "2");

                _Clock.AddMilliseconds(10);
                map.RefreshAll();

                HeartbeatTick();
                Assert.AreEqual(2, map.Count);
            }
        }