Testing Asynchronous Functions with Jest and Handling Promises in React Components
I'm trying to figure out I've looked through the documentation and I'm still confused about I'm trying to test a React component that fetches data from an API using an asynchronous function. The component uses the `useEffect` hook to trigger the fetch on mount. My test fails because the state isn't updated immediately, and I'm receiving a timeout behavior when using `await` with `findBy` queries from `@testing-library/react`. Here's my component: ```javascript import React, { useEffect, useState } from 'react'; const DataFetchingComponent = () => { const [data, setData] = useState(null); const [loading, setLoading] = useState(true); useEffect(() => { const fetchData = async () => { const response = await fetch('https://api.example.com/data'); const result = await response.json(); setData(result); setLoading(false); }; fetchData(); }, []); if (loading) return <div>Loading...</div>; return <div>{JSON.stringify(data)}</div>; }; export default DataFetchingComponent; ``` And here's my test: ```javascript import React from 'react'; import { render, screen } from '@testing-library/react'; import DataFetchingComponent from './DataFetchingComponent'; global.fetch = jest.fn(() => Promise.resolve({ json: () => Promise.resolve([{ id: 1, name: 'Item 1' }]) }) ); test('loads and displays data', async () => { render(<DataFetchingComponent />); const dataElement = await screen.findByText(/Item 1/i); expect(dataElement).toBeInTheDocument(); }); ``` However, when I run the test, it fails with a timeout behavior stating that it couldn't find the text 'Item 1'. I suspect this might be due to the component's initial state, where it renders 'Loading...' before the data is fetched. I've tried increasing the timeout with `jest.setTimeout(10000)` and wrapping the fetch call in `act()`, but nothing seems to work. Any suggestions on how to properly test this asynchronous behavior? Also, I'm using Jest version 27.0.6 and @testing-library/react version 12.0.0. Any ideas what could be causing this? For reference, this is a production service. Any pointers in the right direction? This is happening in both development and production on Windows 11. Any help would be greatly appreciated!