Unable To Mock Node-fetch Using Fetch-mock

I am trying to do unit testing for a simple function which sends a get request, receives a response and then returns a promise object with the success or the failure message. Follo

Solution 1:

If you use node-fetch package, it's not available at the global scope in Node.js. In order to make fetch-mock work you either have to assign fetch to global object (e.g. by import "node-fetch"; instead of import fetch from "node-fetch";) or make fetch injectable to your tested method.

From http://www.wheresrhys.co.uk/fetch-mock/#usageglobal-non-global:

Global or non-global

fetch can be used by your code globally or locally. It’s important to determine which one applies to your codebase as it will impact how you use fetch-mock

Global fetch

In the following scenarios fetch will be a global

• When using native fetch (or a polyfill) in the browser
• When node-fetch has been assigned to global in your Node.js process (a pattern sometimes used in isomorphic codebases)

By default fetch-mock assumes fetch is a global so no more setup is required once you’ve required fetch-mock. Non-global fetch library

In the following scenarios fetch will not be a global

• Using node-fetch in Node.js without assigning to global
• Using fetch-ponyfill in the browser
• Using libraries which use fetch-ponyfill internally
• Some build setups result in a non-global fetch, though it may not always be obvious that this is the case

The sandbox() method returns a function that can be used as a drop-in replacement for fetch. Pass this into your mocking library of choice. The function returned by sandbox() has all the methods of fetch-mock exposed on it, e.g.

const fetchMock = require('fetch-mock');
const myMock = fetchMock.sandbox().mock('/home', 200); // pass myMock in to your application code, instead of fetch, run it, then...
expect(myMock.called('/home')).to.be.true;