如何正确地测试承诺

Question

我使用 Jest 和 React-testing-library 在 React 应用程序中进行了测试：

it('promise test', () => {
    const promise = new Promise<string>(resolve => setTimeout(() => resolve('foo'), 1000))
    expect.assertions(1);
    expect(promise).resolves.toBe('foo');
});

如果我运行测试我得到消息：

Error: expect.assertions(1)
Expected :1
Actual   :0

我的问题是..为什么不调用expect(promise).resolves.toBe('foo')中的代码？如何测试这个异步承诺？

Answer 1

正确的解决方案是：您必须使匿名函数异步并等待响应。

it('promise test', async () => {
    const promise = new Promise<string>(resolve => setTimeout(() => resolve('foo'), 1000))
    expect.assertions(1);
    await expect(promise).resolves.toBe('foo')
});

或者这样

it('promise test', async () => {
    const promise = new Promise<string>(resolve => setTimeout(() => resolve('foo'), 1000))
    expect.assertions(1);
    await promise;
    promise.then(value => {
        expect(value).toBe('foo');
    })
});

如何正确地测试承诺

How to properly test promises

reactjs

jestjs

react-testing-library