public async void ByMachineGuid_Not_Exists()
        {
            var mock = new ServiceMockFacade <IMachineService, IMachineRepository>();

            mock.RepositoryMock.Setup(x => x.ByMachineGuid(It.IsAny <Guid>())).Returns(Task.FromResult <Machine>(null));
            var service = new MachineService(mock.LoggerMock.Object,
                                             mock.MediatorMock.Object,
                                             mock.RepositoryMock.Object,
                                             mock.ModelValidatorMockFactory.MachineModelValidatorMock.Object,
                                             mock.DALMapperMockFactory.DALMachineMapperMock,
                                             mock.DALMapperMockFactory.DALLinkMapperMock);

            ApiMachineServerResponseModel response = await service.ByMachineGuid(default(Guid));

            response.Should().BeNull();
            mock.RepositoryMock.Verify(x => x.ByMachineGuid(It.IsAny <Guid>()));
        }