code: def test_read_main():
      client = TestClient(app)
      response = client.get("/")
      assert response.status_code == 200
      assert response.json() == {"msg": "Hello World"}
  
imports: from fastapi import FastAPI
  from fastapi.testclient import TestClient
  from fastapi.websockets import WebSocket
label_desc: Use image node_id 1 for calling a global function with example usage: test_read_main() without return types