public void Convert_WithInvalidModel_ShouldReturnInvalidModelStateResult() { //Arrange var mockUrlLogic = new Mock <INameCostLogic>(); var controller = new ConvertController(mockUrlLogic.Object); controller.ModelState.AddModelError("", ""); var model = new NameCostModel() { Cost = 1 }; //Act IHttpActionResult actionResult = controller.Convert(model); //Assert actionResult .Should() .BeOfType <InvalidModelStateResult> (because: "model is not valid"); }