运行 promise 后未调用 jest 函数

Question

我正在尝试使用 Jest 和酶解决承诺后测试这些方法。我的组件/功能代码：

// Functional Code
let functionAfterAsync = () => {
  console.log('functionAfterAsync called');
}
const asyncFunction = () => {
  return new Promise(resolve => resolve());
}
const functionWithAsyncCode = () => {
  // ... some more code here
  console.log('functionWithAsyncCode');
  asyncFunction().then((res: any) => {
    functionAfterAsync();
  })
}

我的测试：

functionAfterAsync = jest.fn();
// Tests
describe('<Async Test />', () => {
    it('Call function after promise', () => {
      functionWithAsyncCode();
      expect(functionAfterAsync).toBeCalled();
    })
});

但是functionAfterAsync没有被调用，我得到的错误是： expect(jest.fn()).toBeCalled() Expected mock function to have been called.

有没有办法做到这一点。谢谢您的帮助！！！

Answer 1

在断言已调用之前，您需要等待Promise解决functionAfterAsync。

最简单的方法是返回Promisefrom functionWithAsyncCode：

const functionWithAsyncCode = () => {
  console.log('functionWithAsyncCode');
  return asyncFunction().then(() => {  // return the Promise
    functionAfterAsync();
  })
}

...然后等待它在您的测试中解决：

it('Call function after promise', async () => {  // use an async test function
  await functionWithAsyncCode();  // wait for the Promise to resolve
  expect(functionAfterAsync).toBeCalled();  // SUCCESS
})

或者，您可以在 a 中断言.then并从您的测试函数中返回Promise：

it('Call function after promise', () => {
  return functionWithAsyncCode().then(() => {  // return the Promise
    expect(functionAfterAsync).toBeCalled();  // SUCCESS
  });
})