The following problem can be solved by Live Fields, included in the Power Scripts™ for Jira app. Please also read the documentation regarding accessing the current screen with live fields.
Problem
The default values for fields in the transition screen, can be changed by the user.
Solution
Let's consider we have a rule, by setting the assignee on the resolve issue screen to the reporter. This allows the reporter to test and confirm if the issue is fixed. If so, the reporter should close it.
if(argv["screen"] == "trans_5") {
//On the "Resolve Issue" screen, set the assignee to the reporter
// so the user can test it and confirm that the issue is fixed.
lfSet("assignee", reporter);
lfDisable("assignee");
}
The code above prevents the user to change the value of the assignee.