Testing the Service Locator pattern

To test our implementation of the Service Locator pattern, let's write a client class that we will attach as a component to a GameObject in an empty Unity scene, as follows:

using UnityEngine;

namespace Chapter.ServiceLocator
{
    public class ClientServiceLocator : MonoBehaviour
    {
        void Start() {
            RegisterServices();
        }

        private void RegisterServices() {
            ILoggerService logger = new Logger();
            ServiceLocator.RegisterService(logger);

            IAnalyticsService analytics = new Analytics();
            ServiceLocator.RegisterService(analytics);

            IAdvertisement advertisement = new Advertisement();
            ServiceLocator.RegisterService(advertisement);
        }

        void OnGUI()
        {
            GUILayout.Label("Review output in the console:");

            if (GUILayout.Button("Log Event")) {
                ILoggerService logger = 
                    ServiceLocator...