How to test Chrome Extensions

An average Chrome Extension is HTML5 application, therefore we can test it with Puppetry. The only difference here is in way we obtain the page context. The following walkthrough explains how it can be done

Open Extension Management page

Open Chrome browser.
Navigate to chrome://extensions
Turn on the Developer mode switcher.

Add your extension

Load the unpacked version of your extension. You can create a demo one with extensionizr.com service.
Write down the extension ID (e.g. eclajhagmjdnniapeipnfejgmplgehme) from appeared extension card.

Access the extension in the tests

Launch Puppetry and create an empty test case.
Check the extension manifest.json file for default_popup value (e.g. src/page_action/page_action.html).
Add command page.goto with URL like chrome-extension://EXTENSION_ID/EXTENSION_RELATIVE_URL.
Add command page.screenshot to take a screenshot when the extension HTML is loaded.

Run the tests

Open Run Tests dialog (press F6 or Run in the main menu).
Switch to Browser options and set the Chrome extension folder location (with Browse... button).
Click on Run button.

Observe the report

So we have got the screenshot with Chrome extension page view. Thus we can develop a real test case with commands and assertions pointed at the extension page context.