如何使用 toThrow 和 Jest 断言抛出错误的异步方法 [英] How to assert an async method throwing Error using toThrow with Jest

问题描述

我看到了这个问题，它期望一个 <代码>承诺工作.在我的情况下，Error 在 Promise 之前和之外被抛出.

I have seen this question which expects a Promise to work. In my case the Error is thrown before and outside a Promise.

在这种情况下我如何断言错误?我已经尝试了以下选项.

How can I assert the error in this case? I have tried the options below.

test('Method should throw Error', async () => {

    let throwThis = async () => {
        throw new Error();
    };

    await expect(throwThis).toThrow(Error);
    await expect(throwThis).rejects.toThrow(Error);
});

推荐答案

调用 throwThis 返回一个 Promise 应该用 Error 拒绝，所以语法应该是:

Calling throwThis returns a Promise that should reject with an Error so the syntax should be:

test('Method should throw Error', async () => {

  let throwThis = async () => {
    throw new Error();
  };

  await expect(throwThis()).rejects.toThrow(Error);  // SUCCESS
});

请注意，toThrow 已针对 PR 4884 和 仅适用于 21.3.0+.

Note that toThrow was fixed for promises in PR 4884 and only works in 21.3.0+.

所以这仅在您使用 Jest 22.0.0 或更高版本时有效.

So this will only work if you are using Jest version 22.0.0 or higher.

如果您使用的是早期版本的 Jest，您可以将 spy 传递给 catch:

If you are using an earlier version of Jest you can pass a spy to catch:

test('Method should throw Error', async () => {

  let throwThis = async () => {
    throw new Error();
  };

  const spy = jest.fn();
  await throwThis().catch(spy);
  expect(spy).toHaveBeenCalled();  // SUCCESS
});

...并可选择检查抛出的 Error 通过检查 spy.mock.calls[0][0].

...and optionally check the Error thrown by checking spy.mock.calls[0][0].

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