Hello! Are you running Jira Cloud, Data Center or Server? Yes, it could make a difference. Also, does the issue for testing have a status of "In Test", "Testing", or similar?
There are two easy ways to implement this sort of reporting such that you can use JQL to find the answer you are after. First, you could add a custom field call something like "Test Status" with the Options of:
In Test, Tested, Passed, Failed along with None (i.e., None = Blank).
Then you could search Jira for those options in your query such as "Test Status" = "In Test" to show which Stories as an example are being tested. By the way make sure it is added to the correct screens.
Second method, add to the workflow for the appropriate issues the status of "In Test". Again, you can then search for issues in that "In Test" status.
Either of these methodologies require Jira Administrator privs to implement.
