Web API Controller Unit testing multiple test issue - unit-testing

Question

I have create a web API am have developed some unit tests for it. In one of my controllers I pass in a variable of a Id which runs a stored procedure and returns a list of data with the matching data. Here is one of my unit tests:
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using System.Web.Http.Results;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using WebApi.Controllers;
using WebApi.Models;
namespace UnitTestProject1
{
[TestClass]
public class ProductContollerTests
{
// Unit Test Description: Tests to check the number of returned items with the BrandId = 1 matches the number of Products In testProducts
[TestMethod]
public void GetProducts_ShouldRetrunCorrectProducts()
{
var testProducts = GetTestProducts();
var controller = new ProductsController(testProducts);
var result = controller.GetProducts(1) as List<Product>;
Assert.AreEqual(testProducts.Count, result.Count);
}
private List<Product> GetTestProducts()
{
var testProducts = new List<Product>
{
new Product { BrandId = 1, ProductId = 1, ProductName = "Home" },
new Product { BrandId = 1, ProductId = 2, ProductName = "Motor" },
new Product { BrandId = 1, ProductId = 3, ProductName = "Travel" },
new Product { BrandId = 1, ProductId = 4, ProductName = "Van" },
new Product { BrandId = 1, ProductId = 5, ProductName = "Commercial" }
};
return testProducts;
}
}
}
Current this is passing because I am count the data that is returned and compared to see if it is equal to the data in the list testproducts. Currently this is a unit test for when the brand id is equal to 1. But what happens if I wanted to test for when brand id is equal to 2.
I can add a new product to the list testProducts but this then cause the first test to fails as I am counting the elements in list testProducts so when i add another product e.g.
new Product { BrandId = 2, ProductId = 6, ProductName = "Creditor" }
There are more values in testProducts than the data being returned from my API. Is there a way in which i could add it so that i only count the elements which have a brandId of one so that i could add other tests or will i have to always create a new testproducts List when testing something different.

Answer 1

you are telling this controller to work with a list of five products and then when you call the get method with an ID of 1, which you are not even using by the way, you verify that you get 5 products back.
It's a pointless test, you're not testing anything. I am not even mentioning that you're instantiating a web api controller with a list of items for some strange reason.
Instead, here's what I would do:
I would create a list of items, for real, in an actual database, then call the get brand endpoint and verify that I get back what I should. This would be an integration test which tells you that multiple endpoints are working.
Unit testing is about functionality, changing some data somehow, following a clearly definable method, with clear inputs and outputs.
I would also move away from this idea of instantiating controllers to call methods inside them, instead create proper layers and test those. This is like building a modern API in a webforms way.