public void Test_Get_NonExisting()
        {
            // arrange
            var store = new InMemoryVaryHeaderStore();
            IEnumerable<String> headers = null;

            // act
            var result = store.TryGetValue(TestUrl, out headers);

            // assert
            Assert.IsFalse(result);
            Assert.IsNull(headers);

        }
        public void Test_Insert_Get()
        {
            // arrange
            var store = new InMemoryVaryHeaderStore();
            IEnumerable<String> headers = null;
            var hdrs = new string[] {"a", "b"};

            // act
            store.AddOrUpdate(TestUrl, hdrs);
            var result = store.TryGetValue(TestUrl, out headers);

            // assert
            Assert.IsTrue(result);
            Assert.IsNotNull(headers);
            Assert.AreEqual(hdrs, headers);
        }