public async void SingleApartmentIsNull_NotFoundResult()
        {
            // Arrange
            int apartmentId = 1;
            Mock <ApartmentRepository> mockApartmentRepository = new Mock <ApartmentRepository>();

            mockApartmentRepository
            .Setup(ar => ar.GetAsync(It.IsAny <int>(), It.IsAny <string>()))
            .Returns(Task.FromResult(null as Apartment));

            Mock <IUnitOfWork> mockUnitOfWork = new Mock <IUnitOfWork>();

            mockUnitOfWork
            .Setup(u => u.GetRepository <Apartment, ApartmentRepository>())
            .Returns(mockApartmentRepository.Object);

            ApartmentsController controller = new ApartmentsController(mockUnitOfWork.Object);

            // Act
            IActionResult result = await controller.Single(apartmentId);

            // Assert
            Assert.NotNull(result);
            Assert.IsType <NotFoundResult>(result);
        }
        public async void SingleApartmentIdIsNull_NotFoundResult()
        {
            // Arrange
            Mock <IUnitOfWork> mockUnitOfWork = new Mock <IUnitOfWork>();

            ApartmentsController controller = new ApartmentsController(mockUnitOfWork.Object);

            // Act
            IActionResult result = await controller.Single(null);

            // Assert
            Assert.NotNull(result);
            Assert.IsType <NotFoundResult>(result);
        }