How can I test asynchronous code with Jest?

How can I test asynchronous code with Jest?

You can test asynchronous code in Jest using either callbacks, promises, or async/await syntax. Which one are you using?

I'm using async/await. Can you give me an example?

Sure! You can write a test like this:

test('fetches data', async () => {
  const data = await fetchData();
  expect(data).toBeDefined();
});

This will wait for the fetchData function to resolve before making the assertion.

What if the promise is rejected?

In that case, you can use rejects to test for rejection. For example:

await expect(fetchData()).rejects.toThrow('Error message');

Thanks! Is there a way to mock async functions?

Yes! You can use jest.mock() to mock async functions. Would you like an example of that?