blockdev-test: add test case for drive_add duplicate IDs

The following should work:

  (qemu) drive_add if=none,id=drive0
  (qemu) drive_del drive0
  (qemu) drive_add if=none,id=drive0

Previous versions of QEMU produced a duplicate ID error because
drive_add leaked the options.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

tests/Makefile

@@ -68,6 +68,7 @@ check-qtest-i386-y += tests/rtc-test$(EXESUF)
 check-qtest-i386-y += tests/i440fx-test$(EXESUF)
 check-qtest-i386-y += tests/fw_cfg-test$(EXESUF)
 check-qtest-i386-y += tests/qom-test$(EXESUF)
+check-qtest-i386-y += tests/blockdev-test$(EXESUF)
 check-qtest-x86_64-y = $(check-qtest-i386-y)
 gcov-files-i386-y += i386-softmmu/hw/mc146818rtc.c
 gcov-files-x86_64-y = $(subst i386-softmmu/,x86_64-softmmu/,$(gcov-files-i386-y))
@@ -200,6 +201,7 @@ tests/tmp105-test$(EXESUF): tests/tmp105-test.o $(libqos-omap-obj-y)
 tests/i440fx-test$(EXESUF): tests/i440fx-test.o $(libqos-pc-obj-y)
 tests/fw_cfg-test$(EXESUF): tests/fw_cfg-test.o $(libqos-pc-obj-y)
 tests/qom-test$(EXESUF): tests/qom-test.o
+tests/blockdev-test$(EXESUF): tests/blockdev-test.o $(libqos-pc-obj-y)
 tests/qemu-iotests/socket_scm_helper$(EXESUF): tests/qemu-iotests/socket_scm_helper.o
 
 # QTest rules

tests/blockdev-test.c

@@ -0,0 +1,59 @@
+/*
+ * blockdev.c test cases
+ *
+ * Copyright (C) 2013 Red Hat Inc.
+ *
+ * Authors:
+ *  Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ */
+
+#include <glib.h>
+#include <string.h>
+#include "libqtest.h"
+
+static void test_drive_add_empty(void)
+{
+    QDict *response;
+    const char *response_return;
+
+    /* Start with an empty drive */
+    qtest_start("-drive if=none,id=drive0");
+
+    /* Delete the drive */
+    response = qmp("{\"execute\": \"human-monitor-command\","
+                   " \"arguments\": {"
+                   "   \"command-line\": \"drive_del drive0\""
+                   "}}");
+    g_assert(response);
+    response_return = qdict_get_try_str(response, "return");
+    g_assert(response_return);
+    g_assert(strcmp(response_return, "") == 0);
+    QDECREF(response);
+
+    /* Ensure re-adding the drive works - there should be no duplicate ID error
+     * because the old drive must be gone.
+     */
+    response = qmp("{\"execute\": \"human-monitor-command\","
+                   " \"arguments\": {"
+                   "   \"command-line\": \"drive_add 0 if=none,id=drive0\""
+                   "}}");
+    g_assert(response);
+    response_return = qdict_get_try_str(response, "return");
+    g_assert(response_return);
+    g_assert(strcmp(response_return, "OK\r\n") == 0);
+    QDECREF(response);
+
+    qtest_end();
+}
+
+int main(int argc, char **argv)
+{
+    g_test_init(&argc, &argv, NULL);
+
+    qtest_add_func("/qmp/drive_add_empty", test_drive_add_empty);
+
+    return g_test_run();
+}