public void ReturnEmptyCollection_WhenDontContainingUserId() { // Arrange string userId = "user-id-xx"; var mockedConversationRepository = new Mock <IEFRepository <Conversation> >(); var conversations = new List <Conversation>() { new Conversation() { FirstUserId = "1", SecondUserId = "10" }, new Conversation() { FirstUserId = "2", SecondUserId = "1" }, new Conversation() { FirstUserId = "22", SecondUserId = "5" }, new Conversation() { FirstUserId = "1", SecondUserId = "5" }, new Conversation() { FirstUserId = "51", SecondUserId = "10" }, }.AsQueryable(); mockedConversationRepository.Setup(x => x.All).Returns(conversations); var mockedUnitOfWork = new Mock <IUnitOfWork>(); var mockedConversationFactory = new Mock <IConversationFactory>(); var mockedMessageService = new Mock <IMessageService>(); var conversationService = new ConversationService( mockedConversationRepository.Object, mockedUnitOfWork.Object, mockedConversationFactory.Object, mockedMessageService.Object); // Act var result = conversationService.GetAllByUserId(userId); // Assert CollectionAssert.IsEmpty(result); }