Test the monitor-add, monitor-remove, and query-monitors QMP commands:

- Basic lifecycle: chardev-add -> monitor-add -> query-monitors ->
  monitor-remove -> chardev-remove
- Error: duplicate monitor id
- Error: monitor-remove on nonexistent id
- Error: monitor-add with nonexistent chardev
- Error: second monitor on same chardev (chardev already in use)
- Error: monitor-remove on CLI-created monitor
- Error: monitor-remove on HMP monitor
- Re-add after remove: same id and chardev reusable after removal

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 tests/qtest/qmp-test.c | 186 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 186 insertions(+)

diff --git a/tests/qtest/qmp-test.c b/tests/qtest/qmp-test.c
index edf0886787..5bd57c37cb 100644
--- a/tests/qtest/qmp-test.c
+++ b/tests/qtest/qmp-test.c
@@ -337,6 +337,186 @@ static void test_qmp_missing_any_arg(void)
     qtest_quit(qts);
 }
 
+static void test_qmp_monitor_add_remove(void)
+{
+    QTestState *qts;
+    QDict *resp;
+
+    qts = qtest_init(common_args);
+
+    /* Create a null chardev for the dynamic monitor */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'chardev-add',"
+                     " 'arguments': {'id': 'monitor-chardev',"
+                     "               'backend': {'type': 'null',"
+                     "                           'data': {}}}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    /* Add a dynamic monitor */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-add',"
+                     " 'arguments': {'id': 'dyn-mon',"
+                     "               'chardev': 'monitor-chardev'}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    /* Verify it shows up in query-monitors */
+    resp = qtest_qmp(qts, "{'execute': 'query-monitors'}");
+    g_assert(!qdict_haskey(resp, "error"));
+    qobject_unref(resp);
+
+    /* Error: duplicate id */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-add',"
+                     " 'arguments': {'id': 'dyn-mon',"
+                     "               'chardev': 'monitor-chardev'}}");
+    qmp_expect_error_and_unref(resp, "GenericError");
+
+    /* Remove the dynamic monitor */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-remove',"
+                     " 'arguments': {'id': 'dyn-mon'}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    /* Error: remove nonexistent */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-remove',"
+                     " 'arguments': {'id': 'dyn-mon'}}");
+    qmp_expect_error_and_unref(resp, "GenericError");
+
+    /* Add again after remove -- same id and chardev should work */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-add',"
+                     " 'arguments': {'id': 'dyn-mon',"
+                     "               'chardev': 'monitor-chardev'}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    /* Clean up */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-remove',"
+                     " 'arguments': {'id': 'dyn-mon'}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    resp = qtest_qmp(qts,
+                     "{'execute': 'chardev-remove',"
+                     " 'arguments': {'id': 'monitor-chardev'}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    qtest_quit(qts);
+}
+
+static void test_qmp_monitor_error_paths(void)
+{
+    QTestState *qts;
+    QDict *resp;
+
+    qts = qtest_init(common_args);
+
+    /* Error: chardev does not exist */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-add',"
+                     " 'arguments': {'id': 'bad-mon',"
+                     "               'chardev': 'nonexistent'}}");
+    qmp_expect_error_and_unref(resp, "GenericError");
+
+    /* Error: remove nonexistent monitor */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-remove',"
+                     " 'arguments': {'id': 'bogus'}}");
+    qmp_expect_error_and_unref(resp, "GenericError");
+
+    qtest_quit(qts);
+}
+
+static void test_qmp_monitor_chardev_in_use(void)
+{
+    QTestState *qts;
+    QDict *resp;
+
+    qts = qtest_init(common_args);
+
+    /* Create a null chardev */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'chardev-add',"
+                     " 'arguments': {'id': 'shared-chr',"
+                     "               'backend': {'type': 'null',"
+                     "                           'data': {}}}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    /* Attach first monitor */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-add',"
+                     " 'arguments': {'id': 'mon-1',"
+                     "               'chardev': 'shared-chr'}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    /* Error: second monitor on the same chardev */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-add',"
+                     " 'arguments': {'id': 'mon-2',"
+                     "               'chardev': 'shared-chr'}}");
+    qmp_expect_error_and_unref(resp, "GenericError");
+
+    /* Clean up */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-remove',"
+                     " 'arguments': {'id': 'mon-1'}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    resp = qtest_qmp(qts,
+                     "{'execute': 'chardev-remove',"
+                     " 'arguments': {'id': 'shared-chr'}}");
+    g_assert(qdict_haskey(resp, "return"));
+    qobject_unref(resp);
+
+    qtest_quit(qts);
+}
+
+static void test_qmp_monitor_remove_cli(void)
+{
+    QTestState *qts;
+    QDict *resp;
+
+    /* Launch with a named CLI monitor on a null chardev */
+    qts = qtest_initf("%s -chardev null,id=cli-chr"
+                      " -mon id=cli-mon,chardev=cli-chr,mode=control",
+                      common_args);
+
+    /* Error: monitor-remove must reject CLI-created monitors */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-remove',"
+                     " 'arguments': {'id': 'cli-mon'}}");
+    qmp_expect_error_and_unref(resp, "GenericError");
+
+    qtest_quit(qts);
+}
+
+static void test_qmp_monitor_remove_hmp(void)
+{
+    QTestState *qts;
+    QDict *resp;
+
+    qts = qtest_initf("%s -chardev null,id=hmp-chr"
+                      " -mon id=hmp-mon,chardev=hmp-chr,mode=readline",
+                      common_args);
+
+    /* Error: monitor-remove must reject HMP monitors */
+    resp = qtest_qmp(qts,
+                     "{'execute': 'monitor-remove',"
+                     " 'arguments': {'id': 'hmp-mon'}}");
+    qmp_expect_error_and_unref(resp, "GenericError");
+
+    qtest_quit(qts);
+}
+
 int main(int argc, char *argv[])
 {
     g_test_init(&argc, &argv, NULL);
@@ -348,6 +528,12 @@ int main(int argc, char *argv[])
 #endif
     qtest_add_func("qmp/preconfig", test_qmp_preconfig);
     qtest_add_func("qmp/missing-any-arg", test_qmp_missing_any_arg);
+    qtest_add_func("qmp/monitor-add-remove", test_qmp_monitor_add_remove);
+    qtest_add_func("qmp/monitor-error-paths", test_qmp_monitor_error_paths);
+    qtest_add_func("qmp/monitor-chardev-in-use",
+                    test_qmp_monitor_chardev_in_use);
+    qtest_add_func("qmp/monitor-remove-cli", test_qmp_monitor_remove_cli);
+    qtest_add_func("qmp/monitor-remove-hmp", test_qmp_monitor_remove_hmp);
 
     return g_test_run();
 }

-- 
2.47.3