Maybe workflow does not allow to move directly from "done" to "closed"

You will show bellow workflow configuration

Then the result when i try to close

Then options availables when i select session after, with close statut option

Then result after manually save after change to close status

Message is not blocking : it is just a confirmation.
If you close the Test Session, One Ticket and 1 Activity will also be closed.

You can show that after this capture i click OK

Because in next capture, task disappeared, but not test sessions

And from this situation, if you try and close again the Test Session ?
You should not have confirmation message anymore...
... and then what is result message ?

As wrote before, i can manually close testsession after. but it will be better if testsession can be closed automatically when i close parent

For that, you can update private static $_closeRelationShip and add "TestSession" => "control", to "Activity" array at line 520 of SqlElement.php
Other minor problem, is that status is not updated on close of parent (for all object type). i have a status that is not Idle whereas i have an IdleDate assigned

Thanks

OK, I understand better now.
Fix will be included in patch V8.0.3