Depends on the process. Some of our teams expect reporters to validate fixes (an extension for support type projects - they assume the reporter is happy if it's been resolved for > 2 weeks and automatically close it!). Some have QA by "give it to another developer" and others QA by dedicated QA/Test team.
In many cases you know who needs to test it, but when you don't, you need to get a little inventive. One trick is to add a dummy user like "QA team" which is given an email that goes to the QA group as a whole - they then allocate internally. Another might be to automatically set the target with post functions. Yet another is to nominate a tester early on in the process, with a custom field (a user picker) and then copy that into assignee with a post-function on "pass to QA" transitions.
As for the processes, that's a human thing - it's better to get a process that works for you and then make Jira follow it.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.