Can't access C# Script classes in Unity Test Framework (Unity 2020.2.0b7)

I have a static C# class that I want to test but I’m having trouble accessing the class in my test files.
I’m getting the error: The name ‘SampleClass’ does not exist in the current context [Tests]csharp(CS0103)
Here is what I have done so far.

  1. Create “EditMode” Tests.asmdef file in Tests directory
  2. Create GameAssembly Assembly Definition in my Scripts directory
  3. Add the GameAssembly to Assembly Definition References list in Tests.asmdef.

Is there something I’m missing?

My test file:

using System.Collections;
using System.Collections.Generic;
using NUnit.Framework;
using UnityEngine;
using UnityEngine.TestTools;

public class SampleClassTest
{
    // A Test behaves as an ordinary method
    [Test]
    public void AddTest()
    {
        int result = SampleClass.Add(1, 1);
        Assert.AreEqual(2, result);
    }
}

Tests Assembly config:

GameAssembly config:

So where exactly is SampleClass defined?

It’s defined in Assets/Scripts/ directory