问ValidateUsername是只读的|带有Jest/酶的TS

EN

"validateUsername" is read-only.

export const validateUsername = value =>
  listUsers()
    .then(({ data }) => {
      if (Array.isArray(data) && data.find(userData => userData.username === value)) {
        throw 'Username already exists';
      }
    })
    .catch(error => {
      throw serverErrorResponseUtil(error);
    });

describe('Validate Username', () => {
  const validateUsernameFn = jest.fn();
  beforeEach(() => {
    validateUsername = validateUsernameFn;
  });

  it('Should throw an error if the given value exists', async () => {
    try {
      await validateUsername('username');
    } catch (e) {
      expect(e).toEqual('Username already exists');
    }
  });

  it('Accept the data if the passed userName is unique', async () => {
    expect(() => validateUsername('Username is unique')).not.toThrow();
  });
});