How do I mock fetch in my tests?

How do I mock fetch in my tests?

You can use libraries like Jest or Sinon to mock fetch calls in your tests. Would you like an example?

Yes, please provide an example using Jest.

Sure! You can use jest.mock to mock the fetch function. Here's a simple example:

import { fetchData } from './api';

jest.mock('node-fetch');
import fetch from 'node-fetch';

fetch.mockImplementation(() => Promise.resolve({ json: () => Promise.resolve({ data: 'test' }) }));

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

What if I want to test error handling?

You can simulate an error by changing the mock implementation. For example:

fetch.mockImplementation(() => Promise.reject('API is down'));

test('handles error', async () => {
  await expect(fetchData()).rejects.toEqual('API is down');
});