Javascript TypeError： Cannot read properties of undefined (reading 'then') while Mocking Fetch call in Jest

这是包含fetch调用的文件，它只发送一些本地存储的json文件.

// eslint-disable-next-line import/prefer-default-export
export const get = () => {
  // eslint-disable-next-line no-undef
  return fetch('data/posts.json').then((res) => res.json());
};

在我的测试中，我模拟了fetch方法和Promise.resolve模拟array.

import { get } from './posts';

const mockData = [
  {
    "id": "ig-1",
    "accountId": "IG",
    "accountIcon": "/images/ig-icon.svg",
    "accountName": "IG account",
    "accountImageInitial": "J",
    "imageUrl": "/images/social_logo.png",
    "caption": "test",
    "timestamp": 1635510651638
  },
  {
    "id": "fb-1",
    "accountId": "FB",
    "accountIcon": "/images/fb-icon.svg",
    "accountName": "FB account",
    "accountImageInitial": "J",
    "imageUrl": "/images/social_logo.png",
    "caption": "test",
    "timestamp": 1635510051638
  }
];

global.fetch = jest.fn(() => 
  Promise.resolve({
    json: () => Promise.resolve(mockData)
  })
);

describe('The posts API controller', () => {
  test('get() returns expected default payload', async () => {
    const result = await get();
    expect(fetch).toHaveBeenCalledTimes(1);
    expect(result).toBeTruthy();
  });
});

错误

Type错误: Cannot read properties of undefined (reading 'then')

Type错误: Cannot read properties of undefined (reading 'then')

      2 | export const get = () => {
      3 |   // eslint-disable-next-line no-undef
    > 4 |   return fetch('data/posts.json').then((res) => res.json());
        |          ^
      5 | };

不确定为什么会出现此错误，因为我似乎正确地模拟了fetch？