public void Test_Clear()
        {
            var cacheService = new TestCacheService();

            string res;
            int    count = 0;

            res = cacheService.Test_GetOrAdd(1, x => { count++; return("res"); });
            cacheService.Clear();
            res = cacheService.Test_GetOrAdd(1, x => { count++; return("res"); });
            Assert.That(res, Is.EqualTo("res"));
            Assert.That(count, Is.EqualTo(2));
        }