public async Task GetByIdTest() { _repoWrapper.Setup(r => r.Work.GetFirstOrDefaultAsync(It.IsAny <Expression <Func <Work, bool> > >(), null)).ReturnsAsync(new Work()); var service = new WorkService(_repoWrapper.Object, _mapper.Object); _mapper.Setup(x => x.Map <Work, WorkDTO>(It.IsAny <Work>())).Returns(new WorkDTO()); // Act var result = await service.GetByIdAsync(1); // Assert Assert.NotNull(result); Assert.IsType <WorkDTO>(result); }