Folder structure

assets/Scripts/Game/TestGameRunner.ts

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+import { Component, _decorator } from "cc";
+import { GameRunner } from "../Menu/GameRunner";
+import { delay } from "../Services/Utils/AsyncUtils";
+import { Game } from "./Game";
+const { ccclass } = _decorator;
+
+@ccclass("TestGameRunner")
+export class TestGameRunner extends Component {
+    public start(): void {
+        if (GameRunner.Instance.IsRunning) return;
+        this.playTestGameAsync();
+    }
+
+    public async playTestGameAsync(): Promise<void> {
+        while (Game.Instance == null) await delay(100);
+        Game.Instance.playGame();
+    }
+}

assets/Scripts/Game/TestGameRunner.ts.meta

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+{
+  "ver": "4.0.23",
+  "importer": "typescript",
+  "imported": true,
+  "uuid": "605c7b1b-d7fb-4e85-bdcb-9f102cc45197",
+  "files": [],
+  "subMetas": {},
+  "userData": {}
+}