以下内容来自Jest官网：http://facebook.github.io/jest/docs/en/asynchronous.html

Callback：

test('the data is peanut butter', done => {
  function callback(data) {
    expect(data).toBe('peanut butter');
    done();
  }

  fetchData(callback);
});

Promise成功：

test('the data is peanut butter', () => {
  expect.assertions(1);
  return expect(fetchData()).resolves.toBe('peanut butter');
});

Promise失败：

test('the fetch fails with an error', () => {
  expect.assertions(1);
  return expect(fetchData()).rejects.toMatch('error');
});

Async/Await成功或失败

test('the data is peanut butter', async () => {
  expect.assertions(1);
  await expect(fetchData()).resolves.toBe('peanut butter');
});

test('the fetch fails with an error', async () => {
  expect.assertions(1);
  await expect(fetchData()).rejects.toMatch('error');
});