I’ve seen some people having troubles when it comes to include the test bundle in their Codepen project, so I decided to do this quick tutorial on how to add the test bundle in Codepen.
https://yourwebsite.com/script.js, you will paste the bundle.js URL:
https://cdn.freecodecamp.org/testable-projects-fcc/v1/bundle.js. Save & close the panel and your done. Now you can see the green hamburguer button on the top left corner.
For the visual learners, I made a GIF showing the same steps described above.
Hope it helps some of you!