This project was previously called WebCheck. I posted here on Lobsters about it a few weeks back, how I found problems in TodoMVC implementations using a specification: https://wickstrom.tech/programming/2020/07/02/the-todomvc-showdown-testing-with-webcheck.html
It seems to be using geckodriver, the Firefox implementation of the WebDriver protocol and that’s nice.
But how can it be high-confidence if it tests only in one browser?
Happy to report back with: https://docs.quickstrom.io/running/cross-browser.html
As you say, geckodriver is one implementation of the WebDriver protocol. Consequently, I expect that you could replace geckodriver with another tool that uses that protocol and, bugs notwithstanding, the same tests would run. I suspect the documentation uses geckodriver: using the WebDriver protocol for browser automation suggests a desire for widespread browser compatibility.
While I agree that testing with multiple browsers is valuable and important, it’s not been a big focus so far.
The novelty in Quickstrom lies in the combination of generative testing with DOM introspection and the specification language. I’ve only been building this for the last five months and I’ve had to focus almost exclusively on that part to get something running “end to end”.
I’ve very much planned supporting multiple browsers, and as pointed out, by using WebDriver it shouldn’t be very hard. There’s a lot left to do in this project, for sure. :)