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)); }