test_detox_demo.js

export default class App extends Component {
  constructor(props) {
    super(props);
    this.toggleVisibility = this.toggleVisibility.bind(this);
    this.state = {
      isSecretVisible: false
    };
  }

  toggleVisibility() {
    this.setState({
      isSecretVisible: !this.state.isSecretVisible
    });
  }

  render() {
    return (
      <View testID='mainScreen' style={styles.container}>
        <Button testID='secretButton' 
          style={styles.welcome} 
          onPress={this.toggleVisibility}
          title={'Press to reveal secret'}/>
        {this.state.isSecretVisible && (
          <Image
          testID='secretImage'
          style={{width: 50, height: 50}}
          source={{uri: 'https://facebook.github.io/react-native/docs/assets/favicon.png'}}
        />)}
      </View>
    );
  }
}