aws Auth.currentSession(), catch the error but the error is undefined

I have written a function onLoad() for useEffect(). I used aws-amplify Auth.getCurrentSession(). It cached the exception, but the error is undefined.

async function onLoad() {
try {
  //debugger;
  let session = await Auth.currentSession();
  userHasAuthenticated(true); 
  setUserGroup(session.accessToken.payload['cognito:groups'][0]);
  //get the user group
  await getUserGroup();
}
catch(e) {
  if (e !== 'No current user') {
   // e is undefined
    onError(e);
  }
}
setIsAuthenticating(false);


}

I also want to test the app.js with

test('renders learn react link', () => {
  render(<App/>);
  const linkElement = screen.getByText(/welcome/i);
  expect(linkElement).toBeInTheDocument();
});

App.js return function

  return (
!isAuthenticating && (
  <Router>
  <div className="App">
  .............
    
  </div>
  </Router>
)
  );
}

The problem is IsAuthenticating() set default value is true. The test can't get the document. What should I do to test the document?