tests: add qmp/qom-set-without-value test

test_qom_set_without_value() is about a bug in infrastructure used by
the QMP core, fixed in commit c4897802.  We covered the bug in
infrastructure unit tests (commit bce3035a).  I wrote that test
earlier, to cover QMP level as well, the test could go into qmp-test.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/qmp-test.c

@@ -321,6 +321,19 @@ static void test_qmp_preconfig(void)
     qtest_quit(qs);
 }
 
+static void test_qom_set_without_value(void)
+{
+    QTestState *qts;
+    QDict *resp;
+
+    qts = qtest_init(common_args);
+    resp = qtest_qmp(qts, "{'execute': 'qom-set', 'arguments':"
+                     " { 'path': '/machine', 'property': 'rtc-time' } }");
+    g_assert_nonnull(resp);
+    qmp_assert_error_class(resp, "GenericError");
+    qtest_quit(qts);
+}
+
 int main(int argc, char *argv[])
 {
     g_test_init(&argc, &argv, NULL);
@@ -328,6 +341,7 @@ int main(int argc, char *argv[])
     qtest_add_func("qmp/protocol", test_qmp_protocol);
     qtest_add_func("qmp/oob", test_qmp_oob);
     qtest_add_func("qmp/preconfig", test_qmp_preconfig);
+    qtest_add_func("qmp/qom-set-without-value", test_qom_set_without_value);
 
     return g_test_run();
 }