JIRA uses validators to verify that every input given to a transition is correct before the transition is carried out. The information received on the transition screen from the user might be included as input. If a validator fails, the problem is not moved to the transition’s destination status, the post functions are not run, and the failed validator’s error message is displayed.
There are many different things that validators can check for, including:
If a required field has been completed.
If a field’s value falls inside a predetermined range.
If a field’s value complies with a regular expression.
The uniqueness of a field’s value