public async Task GetAllAsyncWhenNoRequirementsReturnsEmptyCollection() { //Arrange var mockRequirementRepository = GetDefaultIRequirementRepositoryInstance(); var mockUnitOfWork = GetDefaultIUnitOfWorkInstance(); var requirementId = 200; mockRequirementRepository.Setup(r => r.FindById(requirementId)) .Returns(Task.FromResult <Requirement>(null)); var service = new RequirementService(mockRequirementRepository.Object, mockUnitOfWork.Object); //Act RequirementResponse result = await service.GetByIdAsync(requirementId); var message = result.Message; //Assert message.Should().Be("Requirement not found"); }