Tests for the main logic

[muodov]

We've recently added some WTR-based tests for DOM utils (thanks @freiondrej!). The most impactful next step would be to cover the main logic with tests (web.ts).

[freiondrej]

Hey @muodov, I have some remaining work on a side project of mine, but then I’m planning to look into this 🚀

Until then, if anyone gets to this before me, please feel welcome to give it a go, I don’t mean to stop you! 🙌