https://github.com/nshimiye/react-geojson-editor/blob/690605bde78111aa2e5a1aec7d032d4d24d667ae/packages/react-geojson-editor/src/components/GeoJsonEditor/google-map/test/GoogleMap.test.jsx

GoogleMapWithLoader.test.jsx

// @WARNING this is incomplete
class YourComponent extends Component {
  static contextType = GoogleMapContext;
  componentDidMount() {
    if (this.context.map) {
      this.context.map.addListener('click', (e) => { // <= accessing map 
        this.context.map.setCenter(e.latLng); // <= accessing map 
      });
    }
  }
  render() {
    return <div>Access to map instance using GoogleMapContext</div>;
  }
}

describe('GoogleMapWithLoader', () => {
  it('provides map instance to children components', () => {
    const props = {
      googleMapURL: '',
      center: { lat: 0, lng: 0 },
      zoom: 1,
      height: 100,
      width: 100,
    };
    const wrapper = mount(<GoogleMapWithLoader {...props}><YourComponent /></GoogleMapWithLoader>);
    const instance = wrapper.find(YourComponent).instance();
    expect(instance.context.map).toBeInstanceOf(google.maps.Map);
  });
});