函数不是函数,我不知道为什么

我得到了错误 formValidationTest is not a function 在控制台中,单击引发handleSubmit的submit按钮。我不明白为什么我会收到这个信息。有人能解释一下吗。

formValidationTest.js

function formValidationTest(formData) {
  console.log('Test function');

  return true;
}

export default formValidationTest();

路径: Signup.jsx

export default class Signup extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      email: ''
    };

    this.handleSubmit = this.handleSubmit.bind(this);
  }

  handleSubmit(e) {
    e.preventDefault();

    const formErrors = formValidationTest('test');
  }

  render() {
    const { email } = this.props;

    return (
      <div>
        <form className="needs-validation" noValidate>
          <label htmlFor="email">Email</label>
          <input
            type="email"
            id="email"
            aria-describedby="emailHelp"
            placeholder="Email"
            name="email"
            value={email}
            onChange={this.handleInputChange}
          />
          <div className="invalid-feedback">{emailValidationMessage}</div>
          <button type="submit" className="btn btn-primary btn-block" onClick={this.handleSubmit}>
            Sign up
          </button>
        </form>
      </div>
    );
  }
}