GetComponentsTest.cs

using System.Collections.Generic;
using System.Linq;
using UnityEngine;

public class GetsComponentsTest : MonoBehaviour
{
    private IEnumerable<TestClass> testClass;
    // Start is called before the first frame update
    void Start()
    {
        testClass=GetComponents<TestClass>();
        Test();
    }

    public void Test()
    {
        testClass.ToList().ForEach(test=>test.Test());
    }
}