An error in your code is causing the tests to run infinitely. That shouldn’t happen. Bugs can be reported as GitHub Issues. Whenever reporting a bug, please check first that there isn’t already an issue for it and provide as much detail as possible.
I suspect that the problem is that you have your p selector nested in your h1 selector. Since you wouldn’t have a p tag nested in an h1 tag, my guess is that this is your error.
There have historically been infinite testing bugs that only come about if you type things in a particular order, but I don’t think that the tests run automatically anymore, do they?