More than a minute before first of 20k tests is shown as running

[chrmarti]

Testing #24505

All nodes were shown with the progress spinner for over a minute:

Now it is stuck at 34 tests and 97 seconds (duration does not update anymore):

[chrmarti]

Actually, tests are still being run according to the decorations on the tree nodes, just the progress at the top of the tree does not update anymore.

[chrmarti]

And just now also that updated again (after several minutes of not updating):

[chrmarti]

Maybe 20k is just too many. It eventually finished running them and they are displayed correctly.

Maybe worth looking into is why it takes so long initially before the first test is run and to make this phase cancellable (pressing the stop button at that point only takes effect right before the first test would run, but not during the first 90 seconds or so where it seems to be initializing).

[eleanorjboyd]

Thank you for the detailed report here. This has always been a changing problem- just getting all the updates from the subprocess to the UI is consuming and then cancelation also taking a minute. Investigating the cancelation problem as it is connected to another issue reported on slow cancellation and will look into the slow startup since that I don't have a good idea on why it might be happening