public async Task QueueServiceTest_RemoveFromQueue()
        {
            QueueRepositoryMock  repository  = CreateQueueRepository();
            IQueueStorageService serviceTest = new QueueStorageService(repository);

            Assert.ThrowsAsync <ArgumentNullException>(async() => { await serviceTest.RemoveFromQueue(null); });
            var result = await serviceTest.RemoveFromQueue(new DequeuePosition { ServiceType = ServiceType.Nurse });

            Assert.AreEqual(1, result.CustomerNumberInQueue);
        }
        public async Task QueueServiceTest_AddToQueue()
        {
            QueueRepositoryMock  repository  = CreateQueueRepository();
            IQueueStorageService serviceTest = new QueueStorageService(repository);

            Assert.ThrowsAsync <ArgumentNullException>(async() => { await serviceTest.AddToQueue(null); });

            EnqueuePosition testItem = new EnqueuePosition {
                ServiceType = ServiceType.Nurse, UserID = 1313
            };
            var result = await serviceTest.AddToQueue(testItem);

            var queueItem = repository._queueNurse.FirstOrDefault(i => i.UserID == 1313);

            Assert.AreEqual(queueItem.UserNumber, result.UserNumber);
        }