public void ThrowsArgumentNullException_WhenPassedIdDoesntExist() { // Arrange var visitsServiceMock = new Mock <IVisitsService>(); var municipalitiesServiceMock = new Mock <IMunicipalitiesService>(); var usersServiceMock = new Mock <IUserService>(); var pageServiceMock = new Mock <IPageService <Visit> >(); var controller = new VisitsController(visitsServiceMock.Object, municipalitiesServiceMock.Object, usersServiceMock.Object, pageServiceMock.Object); var testId = Guid.NewGuid(); visitsServiceMock.Setup(v => v.GetById(It.IsAny <Guid>())).Returns((Visit)null); // Act & Assert Assert.ThrowsException <ArgumentNullException>(() => controller.Open(testId)); }