public void CustomMemoryCache_AddOrGetExistingCacheAdd()
{
var policy = new CacheItemPolicy {
SlidingExpiration = new TimeSpan(0, 10, 0)
};
var addCache = _customMemoryCache.AddOrGetExisting(Key, Value, policy);
Assert.IsNull(addCache);
var getCacheValue = _customMemoryCache.AddOrGetExisting(Key, Value, policy);
Assert.IsNotNull(getCacheValue);
Assert.AreEqual(Value, getCacheValue);
}