[...]

Indentation is off here.

+            goto cleanup;
+        break;
+    case VIR_DOMAIN_AFFECT_CONFIG:
+        if (virAsprintf(&result_filename,
+                    "%s/qemuhotplugtestdomains/qemuhotplug-%s+%s+config.xml",
+                    abs_srcdir, test->domain_filename,
+                    test->device_filename) < 0)
+            goto cleanup;
+        break;
+    default:

No need to do default in case the switch condition is an enum, although
I'm not sure how that works with flags (non-continuous values).

+        VIR_TEST_VERBOSE("target can either be VIR_DOMAIN_AFFECT_LIVE"
+                         " or VIR_DOMAIN_AFFECT_CONFIG\n");

We should also take into account the fact that it can be both, but
should not be _CURRENT in tests.  That way we don't have to do two lines
of DO_TEST_ATTACH_.  Although that might cause confusion with the 'keep'
parameter.