This. I have nothing against unit testing; there's been times when a unit test (often written by someone else) has stopped me pushing some truly stupid code to production. But when I started developing my canvas library (for fun, not work) I decided early on that unit testing every line of code was not only sucking the joy from the work, but also too hard to cover all the edge cases of what I was trying to deliver: responsive, interactive, animated graphics, often controlled by user interaction with the canvas element. So instead I developed a big bunch of demos which try to cover the full functionality of the library, which I can visually check locally before pushing code changes to the repo[1].

The big drawback is I have to check all these tests/demos manually (across browsers and devices) before releasing a new version of the library into the wild. Automating that process is on my list of Things To Do - if anyone has suggestions/insights into current tooling/testing suites that could help me then I'm very willing to listen and learn!

[1] - https://scrawl-v8.rikweb.org.uk/demonstrations