public void Get_value_for_key()
        {
            var sut = new FilesystemCache(CACHE_PATH);
            sut.ReplaceOrAdd("mykey", "hello");

            Assert.AreEqual("hello", sut.Get("mykey"));
        }
        public void Getting_non_existent_value_causes_exception()
        {
            var sut = new FilesystemCache(CACHE_PATH);

            Assert.Throws<KeyValueStoreException>(() => sut.Get("non existent key"));
        }