async.js

onSubmit={this.props.handleSubmit((values) => {
  return new Promise((resolve, reject) => {
    this.handleSubmitTest(values)
      .then(() => resolve(), err => {
        reject(err);
      });
  }
})}

sync.js

onSubmit={this.props.handleSubmit((values) => {
  return new Promise((resolve, reject) => {
    const errors = this.handleSubmitTest(values);
    
    // You can use lodash to see if it is empty
    if (! isEmpty(errors)) {
      return reject(errors);
    }
    return resolve();
  }
})}