public async Task SearchTest() { var movies = new List <Prescription> { new Prescription() { PatientName = "Dias" }, new Prescription() { PatientName = "Said" }, }; var fakeRepositoryMock = new Mock <IPrescriptionRepository>(); fakeRepositoryMock.Setup(x => x.GetPrescriptionWithPredicate(It.IsAny <Expression <Func <Prescription, bool> > >())).ReturnsAsync(movies); var prescriptionService = new PrescriptionService(fakeRepositoryMock.Object); var resultPrescriptions = await prescriptionService.Search("Dias"); Assert.Collection(resultPrescriptions, prescription => { Assert.Equal("Dias", prescription.PatientName); }, prescription => { Assert.Equal("Said", prescription.PatientName); }); }