Federico Cargnelutti

The package mock-require is useful if you want to mock require statements in Node.js. It has a simple API that allows you to mock anything, from a single exported function to a standard library. Here’s an example:

app/config.js

function init() {
  // ...
}

module.exports = init;

app/services/content.js

import config from '../../config.js';

function load() {
  // ...
}

module.exports = load;

test/services/content_spec.js

import { assert } from "chai";
import sinon from "sinon";
import mockRequire from "mock-require";

describe("My module", () => {
  let module; // module under test
  let configMock;

  beforeEach(() => {
    configMock = {
      init: sinon.stub().returns("foo"),
    };

    // mock es6 import (tip: use the same import path)
    mockRequire("../../config.js", configMock);

    // require es6 module
    module = require("../../../app/services/content.js");
  });

  afterEach(() => {
    // remove all registered mocks
    mockRequire.stopAll();
  });

  describe("Initialisation", () => {
    it("should have an load function", () => {
      assert.isFunction(module.load);
    });
  });
});