I expected the following to find all issues being tested EXCEPT the ones whose label is BeingTestedByCustomer:
(status = Testing) and (labels != BeingTestedByCustomer)
but it says no issues were found.
This fails also:
(status = Testing) AND labels not in (BeingTestedByCustomer)
For reference, please note the results of these related searches:
(status = Testing) AND (labels = BeingTestedByCustomer) finds 2 issues
(status = Testing) AND labels in (BeingTestedByCustomer) finds the same 2 issues
(status = Testing) finds 49 issues