require-poisoning/test.js

Cache-Poisoning applied to Node.js require statements so you inject your own modules

const { describe, it } = require('mocha');
const assume = require('assume');
const poison = require('./');

describe('require-poisoning', function () {
  it('is a function', function () {
    assume(poison).is.a('function');
  });

  it('overriddes an existing require', function () {
    poison('mocha', 'faked');
    assume(require('mocha')).equals('faked');
  });

  it('undo/redo the cache poisoning', function () {
    const undo = poison('assume', 'does not exist');

    assume(require('assume')).equals('does not exist');

    const redo = undo();
    assume(require('assume')).equals(assume);

    const undone = redo();
    assume(require('assume')).equals('does not exist');

    assume(undone()).is.a('function');
    assume(require('assume')).equals(assume);
  });
});