tests: wasapi: check PLAYING -> READY -> PLAYING

Such sequence of state changes is valid and no error should happen.
At the moment, the test fails. Following patches aim to fix it.

Partially based on the code in tests/check/elements/wasapi2.c

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2096>

tests/check/elements/wasapi.c

@@ -0,0 +1,128 @@
+/* GStreamer unit test for wasapi plugin
+ *
+ * Copyright (C) 2021 Jakub Janků <janku.jakub.jj@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gst/gst.h>
+#include <gst/check/gstcheck.h>
+
+typedef struct
+{
+  GMainLoop *loop;
+  GstElement *pipe;
+  guint rem_st_changes;
+} SinkPlayReadyTData;
+
+static gboolean
+bus_watch_cb (GstBus * bus, GstMessage * message, gpointer user_data)
+{
+  fail_unless (message->type != GST_MESSAGE_ERROR);
+  return G_SOURCE_CONTINUE;
+}
+
+static gboolean
+state_timer_cb (gpointer user_data)
+{
+  SinkPlayReadyTData *tdata = user_data;
+  GstState nxt_st = tdata->rem_st_changes % 2 == 1 ?
+      GST_STATE_READY : GST_STATE_PLAYING;
+
+  ASSERT_SET_STATE (tdata->pipe, nxt_st, GST_STATE_CHANGE_SUCCESS);
+  tdata->rem_st_changes--;
+
+  if (tdata->rem_st_changes == 0) {
+    g_main_loop_quit (tdata->loop);
+    return G_SOURCE_REMOVE;
+  }
+  return G_SOURCE_CONTINUE;
+}
+
+/* Test that the wasapisink can survive the state change
+ * from PLAYING to READY and then back to PLAYING */
+GST_START_TEST (test_sink_play_ready)
+{
+  SinkPlayReadyTData tdata;
+  GstBus *bus;
+
+  tdata.pipe = gst_parse_launch ("audiotestsrc ! wasapisink async=false", NULL);
+  fail_unless (tdata.pipe != NULL);
+  bus = gst_element_get_bus (tdata.pipe);
+  fail_unless (bus != NULL);
+  gst_bus_add_watch (bus, bus_watch_cb, NULL);
+
+  ASSERT_SET_STATE (tdata.pipe, GST_STATE_PLAYING, GST_STATE_CHANGE_SUCCESS);
+  tdata.rem_st_changes = 3;     /* -> READY -> PLAYING -> QUIT */
+  g_timeout_add_seconds (1, state_timer_cb, &tdata);
+
+  tdata.loop = g_main_loop_new (NULL, FALSE);
+  g_main_loop_run (tdata.loop);
+
+  g_main_loop_unref (tdata.loop);
+  gst_bus_remove_watch (bus);
+  gst_object_unref (bus);
+  gst_object_unref (tdata.pipe);
+}
+
+GST_END_TEST;
+
+static gboolean
+device_is_available (const gchar * factory_name)
+{
+  GstElement *elem;
+  gboolean avail;
+
+  elem = gst_element_factory_make (factory_name, NULL);
+  if (elem == NULL) {
+    GST_INFO ("%s: not available", factory_name);
+    return FALSE;
+  }
+
+  avail = gst_element_set_state (elem, GST_STATE_READY)
+      == GST_STATE_CHANGE_SUCCESS;
+  if (!avail) {
+    GST_INFO ("%s: cannot change state to ready", factory_name);
+  }
+
+  gst_element_set_state (elem, GST_STATE_NULL);
+  gst_object_unref (elem);
+
+  return avail;
+}
+
+static Suite *
+wasapi_suite (void)
+{
+  Suite *suite = suite_create ("wasapi");
+  TCase *tc_sink = tcase_create ("sink");
+
+  suite_add_tcase (suite, tc_sink);
+
+  if (device_is_available ("wasapisink")) {
+    tcase_add_test (tc_sink, test_sink_play_ready);
+  } else {
+    GST_INFO ("Sink not available, skipping sink tests");
+  }
+
+  return suite;
+}
+
+GST_CHECK_MAIN (wasapi)

tests/check/meson.build

@@ -62,6 +62,7 @@ base_tests = [
   [['elements/viewfinderbin.c']],
   [['elements/vp9parse.c'], false, [gstcodecparsers_dep]],
   [['elements/av1parse.c'], false, [gstcodecparsers_dep]],
+  [['elements/wasapi.c'], host_machine.system() != 'windows', ],
   [['elements/wasapi2.c'], host_machine.system() != 'windows', ],
   [['libs/h264parser.c'], false, [gstcodecparsers_dep]],
   [['libs/h265parser.c'], false, [gstcodecparsers_dep]],