Could you elaborate why it's not possible to start a recording, then run the tests, and then see the data in the low-level overview of the snapshot recorded?
the connection isn't locking anything, the query is. Performance issues also stem from queries locking/doing things, not from connections.
You can start a recording in the realtime tab, record activity, and then look at it and do further analysis. the real time overview doesn't have that info, as it's goal is to give an overview of what's going on at this time, e.g. you run a test / click a button and you see what activity results from that.
Grouping things for the low-level activity requires a period of time and all the activity in that period is then grouped. In real time that wouldn't be possible as the current time hasn't ended so a grouping would be costly.
Recording the snapshot will give you the insight you want. So I suggest you use that feature as it's meant for this situation