React native testing with Typescript and Jest

I am trying to start test with react-native/expo and typescript. I have created an app with the expo's basic typescript template.

To start testing, I followed the expo's documentation on testing with Jest. I have added jest-expo and react-test-renderer as dev dependencies, and have updated the package.json as per the docs:

{"main": "node_modules/expo/AppEntry.js","scripts": {"start": "expo start",    ..."test": "jest"  },"dependencies": {"expo": "~41.0.1","expo-status-bar": "~1.0.4","react": "16.13.1","react-dom": "16.13.1","react-native": "https://github.com/expo/react-native/archive/sdk-41.0.0.tar.gz","react-native-web": "~0.13.12"  },"devDependencies": {"@babel/core": "^7.9.0","@types/jest": "^26.0.23","@types/react": "~16.9.35","@types/react-native": "~0.63.2","@types/react-test-renderer": "^17.0.1","jest-expo": "^41.0.0","react-test-renderer": "^17.0.2","typescript": "~4.0.0"  },"private": true,"jest": {"preset": "jest-expo","transformIgnorePatterns": ["node_modules/(?!(jest-)?react-native|react-clone-referenced-element|@react-native-community|expo(nent)?|@expo(nent)?/.*|react-navigation|@react-navigation/.*|@unimodules/.*|unimodules|sentry-expo|native-base|@sentry/.*)"    ]  }}

This is the test, App.test.tsx:

import renderer from 'react-test-renderer';import App from "../App";import React from "react";describe('<App />', () => {    it('has 1 child', () => {        const tree = renderer.create(<App />).toJSON();        expect(tree.children.length).toBe(1);    });});

In the editor (Webstorm) it is throwing 2 errors:

1. tree Object is possibly 'null'.
2. Property 'children' does not exist on type 'ReactTestRendererJSON | ReactTestRendererJSON[]'. Property 'children' does not exist on type 'ReactTestRendererJSON[]'.

And also, when I run the test, it throws a different error for <App />

renderer.create(<App />).toJSON():

Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: object.

Could you please help me what am I missing here. How to test react native with typescript and jest?