test('good email format', () => {
  const actual = getSignupFormFieldErrors({
    username: 'foo',
    email: 'foo@example.com',
    password: 'pass',
    passwordConfirmation: 'pass',
  });
  const expected = {};
  expect(actual).toEqual(expected);
});
test('bad email format', () => {
  const actual = getSignupFormFieldErrors({
    username: 'foo',
    email: 'foo@example',
    password: 'pass',
    passwordConfirmation: 'pass',
  });
  const expected = {
    email: BAD_FORMAT,
  };
  expect(actual).toEqual(expected);
});