fetch-mock未Mock请求却调用真实API，导入报错求助（Jest+Babel环境）

Hey there, let's break down and solve the two problems you're hitting with fetch-mock:

1. Mock isn't working (real API is being called instead) #

This usually happens because fetch-mock isn't properly overriding the fetch instance your code is using. Here's how to fix it:

Check how you're using fetch in your code #

• If your code relies on the global fetch: You need to explicitly assign the fetch-mock sandbox to global.fetch before each test.
• If you're importing fetch from a module (like node-fetch): You'll need to use Jest's mocking to replace that import with fetch-mock.

Example for global fetch

const fetchMock = require('fetch-mock/es5/server');

beforeEach(() => {
  // Reset mocks between tests to avoid cross-test contamination
  fetchMock.reset();
  // Replace global fetch with fetch-mock's sandboxed instance
  global.fetch = fetchMock.sandbox();
});

test('should return mocked data instead of hitting real API', () => {
  // Set up your mock response
  global.fetch.get('/your-api-endpoint', [{ key: 'val1' }, { key: 'val2' }]);

  // Call your function that uses fetch
  return yourApiClient.getData().then(response => {
    // Verify you got the mocked data
    expect(response).toEqual([{ key: 'val1' }, { key: 'val2' }]);
    // Verify the mock was called (not the real API)
    expect(global.fetch.called('/your-api-endpoint')).toBe(true);
  });
});

Additional checks #

• Double-check that the mock's URL exactly matches the URL your code is requesting (including base URLs, query params, or trailing slashes).
• Make sure you set up the mock before calling the function that triggers the fetch request.

2. Error when using fetch-mock instead of fetch-mock/es5/server #

Node v6.13.0 has limited support for ES6+ syntax, and the main fetch-mock module uses modern ES6 exports that Node 6 can't parse without extra transpilation. The /es5/server entry is specifically compiled to ES5 for compatibility with older Node versions like yours.

Solution #

Stick with require('fetch-mock/es5/server') (or import fetchMock from 'fetch-mock/es5/server' if your Babel is set up to handle it). Avoid importing the main fetch-mock module directly—this is the intended way to use fetch-mock with Node 6.

If you really want to use the main module, you'd need to configure Babel to transpile fetch-mock in your Jest settings, but this is more complex and unnecessary when the ES5 entry exists.

Final Notes #

• Ensure you're using a version of fetch-mock that supports Node 6 (versions like v8.x are known to work; newer versions may drop support).
• Always reset your mocks between tests to prevent state leakage.

内容的提问来源于stack exchange，提问作者vamsiampolu