React Unit Testing Example 11

LoadingIndicator.js

export default class LoadingIndicator extends Component {
  static propTypes = {
    isLoading: PropTypes.bool.isRequired,
  };

  state = {
    isPastDelay: false
  };

  componentDidMount () {
    this._delayTimer = setTimeout(
      () => this.setState({ isPastDelay: true }), 200
    );
  }

  render() {
    if (this.props.isLoading) {
      if (!this.state.isPastDelay) {
        return null;
      }
      return <div>loading...</div>;
    }
    return this.props.children;
  }
}