public async Task Create_When_Filter_Already_Exist_Then_Operation_Details_False() { //arrange var expectedResult = new OperationDetails(false, $"You already have a filter with name \"{filterDto.FilterName}\"", ""); unitOfWork .Setup(u => u.Filters.SingleOrDefault(It.Is <Func <Filter, bool> >(i => i(filter)))) .Returns(filter); //act var actualResult = await underTest.Create(filterDto); //assert Assert.AreEqual(expectedResult.Succeeded, actualResult.Succeeded); }