Play mode tests public property initialization.

I am new to unity testing and am running into some issues.
I am testing but find that I have to initialize the properties of each component (monobehaviour). Why is that? enableOnZero;

Consider this. An Placement task has a delegate that occurs on correct execution. A countdown subscriber observes the placement task and decrements accordingly. Once the timer hits zero it executes the EnableDisableBehavior which enables gameobjects. The designer specifies these object. How do I test this since the designer only specifies it in the editor?

Code (CSharp):

1. public class EnableOnComplete : MonoBehaviour
2.     {
3.         [SerializeField] public OnComplete subject;
4.         public GameObject[] enableOnZero;
5.         public GameObject[] disableOnZero;
6.  
7.  
8.         public void EnableAndDisable()
9.         {
10.             foreach (GameObject obj in enableOnZero)
11.             {
12.          
13.                 obj.SetActive(true);
14.             }
15.             foreach (GameObject obj in disableOnZero)
16.             {
17.          
18.                 obj.SetActive(false);
19.             }
20.         }
21.     }

Code (CSharp):

1. [UnityTest]
2.         public IEnumerator EnableOnCompleteTestWithEnumeratorPasses()
3.         {
4.             yield return TestSetup();
5.  
6.             countdownOnComplete.counter = 2;
7.  
8.             _enableOnComplete.enableOnZero = new GameObject[1];
9.             _enableOnComplete.enableOnZero[0] = enableCompleted;
10.             // _enableOnComplete.disableOnZero = new GameObject[0];
11.             enableCompleted.SetActive(false);
12.             yield return null;
13.  
14.             Assert.IsFalse(enableCompleted.activeInHierarchy);
15.  
16.             placementTask.onCorrectCompletion.Invoke();
17.             yield return null; //1
18.             Assert.IsFalse(enableCompleted.activeInHierarchy);
19.  
20.             placementTask.onCorrectCompletion.Invoke();
21.             yield return null; //0
22.             Assert.IsTrue(enableCompleted.activeInHierarchy);
23.  
24.             placementTask.onCorrectCompletion.Invoke();
25.             yield return null; //unchanged
26.             Assert.IsTrue(enableCompleted.activeInHierarchy);
27.  
28.             yield return null;
29.         }

1. Why do I have to initialize disableOnZero? I thought since I am using play mode tests the editor would do that for me?
2. How can I make this private serializefield and still insert and gameobject to enable and disable in order to test it?
3. Is there something I missing in the steps. Create gameobject -> attach component -> attach testable hypothetical object -> predict outcome?

 

https://forum.unity.com/threads/uni...s-set-from-the-inspector.594451/#post-3971452
,posted 2 some solutions. Basically (1) move some test code into the class or (2) do some

I found that creating a testing prefab loading it worked better.

[SerializeField] private GameObject testPrefab = (GameObject) Resources.Load("Testing/EnableOnCompleteTask");

After consulting unity resources I find