public void UpdateWithValidDataShouldReturnOk()
 {
     var controller = new CategoriesController(categories);
     var result = controller.Update(1, "new title");
     var okResult = result as OkResult;
     Assert.IsNotNull(okResult, "Update with valid id should return OK");
 }
 public void UpdateWithNotExistingCategoryShouldReturnBadRequest()
 {
     var controller = new CategoriesController(categories);
     var result = controller.Update(120, "fail");
     var badResult = result as BadRequestErrorMessageResult;
     Assert.IsNotNull(badResult, "Update with invalid id should return bad request");
 }