You can do some customization to fill the value into a custom entity field and be able to search on that.
-Create the field
-Modify workflow to populate the field with the Test ID on entry into the test
<font class="small">Code:</font><hr /><pre>
On Error Resume Next
Test_Fields.Field("TS_USER_XX").Value = _
On Error GoTo 0
(*) TS_USER_XX is the custom field you have created to assign the TS_TEST_IS value to -