Postponed on ✨ Add OpenTelemetry Application Performance Monitoring to core performance tests Fixed .
We can probably do someting to measure page interactions, which would help core/sites improve https://web.dev/inp/ and https://web.dev/fid/
Trying to think of what a minimum test case for core would look like I came up with the following:
1. AJAX-enable a view with a pager in core, the front page, taxonomy/term/%, admin/content
2. In the test, we'd need to subclass ::clickLink(), reset the performance log, then extract the first paint event from the log. We'd also need to figure out when to time from the link being clicked (unless this is also available from the performance log, which would be useful if it is).
You could then for example have a test with the AJAX-enabled pager, a test with a non-AJAX-enabled pager (so requiring a full page refresh), and we could revert the AJAX GET requests patch and test with that. Although the next paint for AJAX ought to be the spinner, so would expect this to be the same for POST and GET since it's measuring any initial feedback, not the end of the interaction.
Another possible example would be opening the media library on a node form.
Related to this is we would ideally be able to test the performance of form submissions - login form, entity forms etc. Currently the tests only handle drupalGet().