Getting ReferenceError: fetch is not defined

Question

In my Saga test for my react native application (that does work correctly) I have added the following test that calls a function that perform a POST http call (doScan).

describe('Scan the product and register the scanning action', () => {
  const it = sagaHelper(scanProductSaga(scanProductAction(item)));

  it('logscan via ASL', (result) => {
    expect(result).toEqual(cps(ASLogger.logScan, xxx));
    return logScanResult;
  });

  it('should register the product', (result) => {
    expect(result).toEqual(call(doScan, logScanResult));
  });
});

Separate file:

const doScan = scanObj =>
  toJSON(fetch('https://xxxx.xxxxxx.com/logger/scans', {
    method: 'POST',
    headers: new Headers(CONTENT_TYPE_HEADERS),
    body: JSON.stringify(scanObj),
  }));

Note: the fetch function is from 'react-native-interfaces.js' within the react-native library. The test fails and the error is caused by the following exception :

ReferenceError: fetch is not defined
      at doScan (/Users/andy/WebstormProjects/ASAP/api/index.js:81:11)....

What can cause such issue? What the solution may be?

Answer 1

react-native has fetch default, but test environment on node.js does not have fetch.

You can import fetch like following at the top of test code.

const fetch = require('node-fetch')

---

The file react-native-interface.js only declare the type of fetch.

declare var fetch: any;