Working on several chrome extensions I came up with sinon-chrome project that allows to run unit-tests using mocha, nodejs and phantomjs.

Basically, it creates sinon mocks of all chrome.* API where you can put any predefined json responses.

Next, you load your scripts using node’s vm.runInNewContext for background page and phantomjs for render popup / options page.

And finally, you assert that chrome api was called with needed arguments.

Let’s take an example:
Assume we have simple chrome extension that displays number of opened tabs in button badge.

background page:

chrome.tabs.query({}, function(tabs) {
  chrome.browserAction.setBadgeText({text: String(tabs.length)});
});

To test it we need:

1. mock chrome.tabs.query to return predefined response, e.g. two tabs.
2. inject our mocked chrome.* api into some environment
3. run our extension code in this environment
4. assert that button badge equals to ‘2’

The code snippet is following:

const vm = require('vm');
const fs = require('fs');
const chrome = require('sinon-chrome');

// 1. mock `chrome.tabs.query` to return predefined response 
chrome.tabs.query.yields([
  {id: 1, title: 'Tab 1'}, 
  {id: 2, title: 'Tab 2'}
]);

// 2. inject our mocked chrome.* api into some environment
const context = {
  chrome: chrome
};

// 3. run our extension code in this environment
const code = fs.readFileSync('src/background.js');
vm.runInNewContext(code, context);

// 4. assert that button badge equals to '2'
sinon.assert.calledOnce(chrome.browserAction.setBadgeText);
sinon.assert.calledWithMatch(chrome.browserAction.setBadgeText, {
  text: "2"
});

Now we can wrap it into mocha’s describe..it functions and run from terminal:

$ mocha

background page
  ✓ should display opened tabs count in button badge

1 passing (98ms)

You can find full example here.

Additionally, sinon-chrome allows to trigger any chrome event with predefined response, e.g.

chrome.tab.onCreated.trigger({url: 'http://google.com'});