public async void ByExternalId_Not_Exists() { var mock = new ServiceMockFacade <ILinkService, ILinkRepository>(); mock.RepositoryMock.Setup(x => x.ByExternalId(It.IsAny <Guid>())).Returns(Task.FromResult <Link>(null)); var service = new LinkService(mock.LoggerMock.Object, mock.MediatorMock.Object, mock.RepositoryMock.Object, mock.ModelValidatorMockFactory.LinkModelValidatorMock.Object, mock.DALMapperMockFactory.DALLinkMapperMock, mock.DALMapperMockFactory.DALLinkLogMapperMock); ApiLinkServerResponseModel response = await service.ByExternalId(default(Guid)); response.Should().BeNull(); mock.RepositoryMock.Verify(x => x.ByExternalId(It.IsAny <Guid>())); }