Merge branch 'backport-3113-action-crashes' into 'glib-2-74'

Backport !3113 “gaction: Validate actions activated over D-Bus” to glib-2-74

See merge request GNOME/glib!3114

13 files changed, 1370 insertions, 170 deletions

diff --git a/gio/gactiongroupexporter.c b/gio/gactiongroupexporter.c
index 575a03ca2..3bc2f0418 100644
--- a/gio/gactiongroupexporter.c
+++ b/gio/gactiongroupexporter.c
@@ -433,11 +433,37 @@ org_gtk_Actions_method_call (GDBusConnection       *connection,
       GVariant *platform_data;
       GVariantIter *iter;
       const gchar *name;
+      const GVariantType *parameter_type = NULL;
 
       g_variant_get (parameters, "(&sav@a{sv})", &name, &iter, &platform_data);
       g_variant_iter_next (iter, "v", &parameter);
       g_variant_iter_free (iter);
 
+      /* Check the action exists and the parameter type matches. */
+      if (!g_action_group_query_action (exporter->action_group,
+                                        name, NULL, &parameter_type,
+                                        NULL, NULL, NULL))
+        {
+          g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
+                                                 "Unknown action ‘%s’", name);
+          g_clear_pointer (&parameter, g_variant_unref);
+          g_variant_unref (platform_data);
+          return;
+        }
+
+      if (!((parameter_type == NULL && parameter == NULL) ||
+            (parameter_type != NULL && parameter != NULL && g_variant_is_of_type (parameter, parameter_type))))
+        {
+          g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
+                                                 "Invalid parameter for action ‘%s’: expected type %s but got type %s",
+                                                 name,
+                                                 (parameter_type != NULL) ? (const gchar *) parameter_type : "()",
+                                                 (parameter != NULL) ? g_variant_get_type_string (parameter) : "()");
+          g_clear_pointer (&parameter, g_variant_unref);
+          g_variant_unref (platform_data);
+          return;
+        }
+
       if (G_IS_REMOTE_ACTION_GROUP (exporter->action_group))
         g_remote_action_group_activate_action_full (G_REMOTE_ACTION_GROUP (exporter->action_group),
                                                     name, parameter, platform_data);
@@ -455,9 +481,43 @@ org_gtk_Actions_method_call (GDBusConnection       *connection,
       GVariant *platform_data;
       const gchar *name;
       GVariant *state;
+      const GVariantType *state_type = NULL;
 
       g_variant_get (parameters, "(&sv@a{sv})", &name, &state, &platform_data);
 
+      /* Check the action exists and the state type matches. */
+      if (!g_action_group_query_action (exporter->action_group,
+                                        name, NULL, NULL,
+                                        &state_type, NULL, NULL))
+        {
+          g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
+                                                 "Unknown action ‘%s’", name);
+          g_variant_unref (state);
+          g_variant_unref (platform_data);
+          return;
+        }
+
+      if (state_type == NULL)
+        {
+          g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
+                                                 "Cannot change state of action ‘%s’ as it is stateless", name);
+          g_variant_unref (state);
+          g_variant_unref (platform_data);
+          return;
+        }
+
+      if (!g_variant_is_of_type (state, state_type))
+        {
+          g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
+                                                 "Invalid state for action ‘%s’: expected type %s but got type %s",
+                                                 name,
+                                                 (const gchar *) state_type,
+                                                 g_variant_get_type_string (state));
+          g_variant_unref (state);
+          g_variant_unref (platform_data);
+          return;
+        }
+
       if (G_IS_REMOTE_ACTION_GROUP (exporter->action_group))
         g_remote_action_group_change_action_state_full (G_REMOTE_ACTION_GROUP (exporter->action_group),
                                                         name, state, platform_data);
diff --git a/gio/gapplication.c b/gio/gapplication.c
index 1d602c763..3708e812c 100644
--- a/gio/gapplication.c
+++ b/gio/gapplication.c
@@ -673,6 +673,8 @@ add_packed_option (GApplication *application,
  * inspected and modified.  If %G_APPLICATION_HANDLES_COMMAND_LINE is
  * set, then the resulting dictionary is sent to the primary instance,
  * where g_application_command_line_get_options_dict() will return it.
+ * As it has been passed outside the process at this point, the types of all
+ * values in the options dict must be checked before being used.
  * This "packing" is done according to the type of the argument --
  * booleans for normal flags, strings for strings, bytestrings for
  * filenames, etc.  The packing only occurs if the flag is given (ie: we
diff --git a/gio/gapplication.h b/gio/gapplication.h
index 345405366..70074349a 100644
--- a/gio/gapplication.h
+++ b/gio/gapplication.h
@@ -95,8 +95,11 @@ struct _GApplicationClass
                                                      gchar                   ***arguments,
                                                      int                       *exit_status);
 
+  /* @platform_data comes from an external process and is untrusted. All value types
+   * must be validated before being used. */
   void                      (* before_emit)         (GApplication              *application,
                                                      GVariant                  *platform_data);
+  /* Same as for @before_emit. */
   void                      (* after_emit)          (GApplication              *application,
                                                      GVariant                  *platform_data);
   void                      (* add_platform_data)   (GApplication              *application,
diff --git a/gio/gapplicationcommandline.c b/gio/gapplicationcommandline.c
index 9fe52da5d..ef6c2d2a3 100644
--- a/gio/gapplicationcommandline.c
+++ b/gio/gapplicationcommandline.c
@@ -260,20 +260,20 @@ grok_platform_data (GApplicationCommandLine *cmdline)
   g_variant_iter_init (&iter, cmdline->priv->platform_data);
 
   while (g_variant_iter_loop (&iter, "{&sv}", &key, &value))
-    if (strcmp (key, "cwd") == 0)
+    if (strcmp (key, "cwd") == 0 && g_variant_is_of_type (value, G_VARIANT_TYPE_BYTESTRING))
       {
         if (!cmdline->priv->cwd)
           cmdline->priv->cwd = g_variant_dup_bytestring (value, NULL);
       }
 
-    else if (strcmp (key, "environ") == 0)
+    else if (strcmp (key, "environ") == 0 && g_variant_is_of_type (value, G_VARIANT_TYPE_BYTESTRING_ARRAY))
       {
         if (!cmdline->priv->environ)
           cmdline->priv->environ =
             g_variant_dup_bytestring_array (value, NULL);
       }
 
-    else if (strcmp (key, "options") == 0)
+    else if (strcmp (key, "options") == 0 && g_variant_is_of_type (value, G_VARIANT_TYPE_VARDICT))
       {
         if (!cmdline->priv->options)
           cmdline->priv->options = g_variant_ref (value);
@@ -507,6 +507,9 @@ g_application_command_line_get_arguments (GApplicationCommandLine *cmdline,
  * If no options were sent then an empty dictionary is returned so that
  * you don't need to check for %NULL.
  *
+ * The data has been passed via an untrusted external process, so the types of
+ * all values must be checked before being used.
+ *
  * Returns: (transfer none): a #GVariantDict with the options
  *
  * Since: 2.40
@@ -793,6 +796,9 @@ g_application_command_line_get_exit_status (GApplicationCommandLine *cmdline)
  * information like the current working directory and the startup
  * notification ID.
  *
+ * It comes from an untrusted external process and hence the types of all
+ * values must be validated before being used.
+ *
  * For local invocation, it will be %NULL.
  *
  * Returns: (nullable): the platform data, or %NULL
diff --git a/gio/gapplicationimpl-dbus.c b/gio/gapplicationimpl-dbus.c
index bcad19d2e..ac6644d88 100644
--- a/gio/gapplicationimpl-dbus.c
+++ b/gio/gapplicationimpl-dbus.c
@@ -286,6 +286,7 @@ g_application_impl_method_call (GDBusConnection       *connection,
       GVariant *platform_data;
       GVariantIter *iter;
       const gchar *name;
+      const GVariantType *parameter_type = NULL;
 
       /* Only on the freedesktop interface */
 
@@ -293,6 +294,31 @@ g_application_impl_method_call (GDBusConnection       *connection,
       g_variant_iter_next (iter, "v", &parameter);
       g_variant_iter_free (iter);
 
+      /* Check the action exists and the parameter type matches. */
+      if (!g_action_group_query_action (impl->exported_actions,
+                                        name, NULL, &parameter_type,
+                                        NULL, NULL, NULL))
+        {
+          g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
+                                                 "Unknown action ‘%s’", name);
+          g_clear_pointer (&parameter, g_variant_unref);
+          g_variant_unref (platform_data);
+          return;
+        }
+
+      if (!((parameter_type == NULL && parameter == NULL) ||
+            (parameter_type != NULL && parameter != NULL && g_variant_is_of_type (parameter, parameter_type))))
+        {
+          g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
+                                                 "Invalid parameter for action ‘%s’: expected type %s but got type %s",
+                                                 name,
+                                                 (parameter_type != NULL) ? (const gchar *) parameter_type : "()",
+                                                 (parameter != NULL) ? g_variant_get_type_string (parameter) : "()");
+          g_clear_pointer (&parameter, g_variant_unref);
+          g_variant_unref (platform_data);
+          return;
+        }
+
       class->before_emit (impl->app, platform_data);
       g_action_group_activate_action (impl->exported_actions, name, parameter);
       class->after_emit (impl->app, platform_data);
diff --git a/gio/gfdonotificationbackend.c b/gio/gfdonotificationbackend.c
index e0bfea535..594ed9966 100644
--- a/gio/gfdonotificationbackend.c
+++ b/gio/gfdonotificationbackend.c
@@ -63,8 +63,8 @@ typedef struct
   GFdoNotificationBackend *backend;
   gchar *id;
   guint32 notify_id;
-  gchar *default_action;
-  GVariant *default_action_target;
+  gchar *default_action;  /* (nullable) (owned) */
+  GVariant *default_action_target;  /* (nullable) (owned), not floating */
 } FreedesktopNotification;
 
 static void
@@ -131,22 +131,40 @@ g_fdo_notification_backend_find_notification_by_notify_id (GFdoNotificationBacke
   return NULL;
 }
 
-static void
+static gboolean
 activate_action (GFdoNotificationBackend *backend,
                  const gchar             *name,
                  GVariant                *parameter)
 {
   GNotificationBackend *g_backend = G_NOTIFICATION_BACKEND (backend);
 
-  if (name)
+  /* Callers should not provide a floating variant here */
+  g_assert (parameter == NULL || !g_variant_is_floating (parameter));
+
+  if (name != NULL &&
+      g_str_has_prefix (name, "app."))
     {
-      if (g_str_has_prefix (name, "app."))
-        g_action_group_activate_action (G_ACTION_GROUP (g_backend->application), name + 4, parameter);
+      const GVariantType *parameter_type = NULL;
+      const gchar *action_name = name + strlen ("app.");
+
+      /* @name and @parameter come as untrusted input over D-Bus, so validate them first */
+      if (g_action_group_query_action (G_ACTION_GROUP (g_backend->application),
+                                       action_name, NULL, &parameter_type,
+                                       NULL, NULL, NULL) &&
+          ((parameter_type == NULL && parameter == NULL) ||
+           (parameter_type != NULL && parameter != NULL && g_variant_is_of_type (parameter, parameter_type))))
+        {
+          g_action_group_activate_action (G_ACTION_GROUP (g_backend->application), action_name, parameter);
+          return TRUE;
+        }
     }
-  else
+  else if (name == NULL)
     {
       g_application_activate (g_backend->application);
+      return TRUE;
     }
+
+  return FALSE;
 }
 
 static void
@@ -162,6 +180,7 @@ notify_signal (GDBusConnection *connection,
   guint32 id = 0;
   const gchar *action = NULL;
   FreedesktopNotification *n;
+  gboolean notification_closed = TRUE;
 
   if (g_str_equal (signal_name, "NotificationClosed") &&
       g_variant_is_of_type (parameters, G_VARIANT_TYPE ("(uu)")))
@@ -184,29 +203,39 @@ notify_signal (GDBusConnection *connection,
     {
       if (g_str_equal (action, "default"))
         {
-          activate_action (backend, n->default_action, n->default_action_target);
+          if (!activate_action (backend, n->default_action, n->default_action_target))
+            notification_closed = FALSE;
         }
       else
         {
-          gchar *name;
-          GVariant *target;
-
-          if (g_action_parse_detailed_name (action, &name, &target, NULL))
-            {
-              activate_action (backend, name, target);
-              g_free (name);
-              if (target)
-                g_variant_unref (target);
-            }
+          gchar *name = NULL;
+          GVariant *target = NULL;
+
+          if (!g_action_parse_detailed_name (action, &name, &target, NULL) ||
+              !activate_action (backend, name, target))
+            notification_closed = FALSE;
+
+          g_free (name);
+          g_clear_pointer (&target, g_variant_unref);
         }
     }
 
-  /* Get the notification again in case the action redrew it */
-  n = g_fdo_notification_backend_find_notification_by_notify_id (backend, id);
-  if (n != NULL)
+  /* Remove the notification, as it’s either been explicitly closed
+   * (`NotificationClosed` signal) or has been closed as a result of activating
+   * an action successfully. GLib doesn’t currently support the `resident` hint
+   * on notifications which would allow them to stay around after having an
+   * action invoked on them (see
+   * https://specifications.freedesktop.org/notification-spec/notification-spec-latest.html#idm45877717456448)
+   *
+   * First, get the notification again in case the action redrew it */
+  if (notification_closed)
     {
-      backend->notifications = g_slist_remove (backend->notifications, n);
-      freedesktop_notification_free (n);
+      n = g_fdo_notification_backend_find_notification_by_notify_id (backend, id);
+      if (n != NULL)
+        {
+          backend->notifications = g_slist_remove (backend->notifications, n);
+          freedesktop_notification_free (n);
+        }
     }
 }
 
diff --git a/gio/gnotificationbackend.c b/gio/gnotificationbackend.c
index e5f404705..acbd10820 100644
--- a/gio/gnotificationbackend.c
+++ b/gio/gnotificationbackend.c
@@ -29,8 +29,22 @@
 G_DEFINE_TYPE (GNotificationBackend, g_notification_backend, G_TYPE_OBJECT)
 
 static void
+g_notification_backend_dispose (GObject *obj)
+{
+  GNotificationBackend *backend = G_NOTIFICATION_BACKEND (obj);
+
+  backend->application = NULL;  /* no reference held, but clear the pointer anyway to avoid it dangling */
+  g_clear_object (&backend->dbus_connection);
+
+  G_OBJECT_CLASS (g_notification_backend_parent_class)->dispose (obj);
+}
+
+static void
 g_notification_backend_class_init (GNotificationBackendClass *class)
 {
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+
+  object_class->dispose = g_notification_backend_dispose;
 }
 
 static void
diff --git a/gio/gtestdbus.c b/gio/gtestdbus.c
index cf7d1a4b8..6aedb3eae 100644
--- a/gio/gtestdbus.c
+++ b/gio/gtestdbus.c
@@ -94,7 +94,7 @@ _g_object_unref_and_wait_weak_notify (gpointer object)
   g_idle_add (unref_on_idle, object);
 
   /* Make sure we don't block forever */
-  timeout_id = g_timeout_add (30 * 1000, on_weak_notify_timeout, &data);
+  timeout_id = g_timeout_add_seconds (30, on_weak_notify_timeout, &data);
 
   g_main_loop_run (data.loop);
 
diff --git a/gio/tests/actions.c b/gio/tests/actions.c
index f27841b4b..0bd63634b 100644
--- a/gio/tests/actions.c
+++ b/gio/tests/actions.c
@@ -2,6 +2,7 @@
  * Copyright © 2010, 2011, 2013, 2014 Codethink Limited
  * Copyright © 2010, 2011, 2012, 2013, 2015 Red Hat, Inc.
  * Copyright © 2012 Pavel Vasin
+ * Copyright © 2022 Endless OS Foundation, LLC
  *
  * SPDX-License-Identifier: LGPL-2.1-or-later
  *
@@ -189,6 +190,22 @@ strv_set_equal (const gchar * const *strv, ...)
   return res;
 }
 
+static void
+ensure_state (GActionGroup *group,
+              const gchar  *action_name,
+              const gchar  *expected)
+{
+  GVariant *value;
+  gchar *printed;
+
+  value = g_action_group_get_action_state (group, action_name);
+  printed = g_variant_print (value, TRUE);
+  g_variant_unref (value);
+
+  g_assert_cmpstr (printed, ==, expected);
+  g_free (printed);
+}
+
 G_GNUC_BEGIN_IGNORE_DEPRECATIONS
 
 static void
@@ -644,11 +661,13 @@ compare_action_groups (GActionGroup *a, GActionGroup *b)
 }
 
 static gboolean
-stop_loop (gpointer data)
+timeout_cb (gpointer user_data)
 {
-  GMainLoop *loop = data;
+  gboolean *timed_out = user_data;
 
-  g_main_loop_quit (loop);
+  g_assert_false (*timed_out);
+  *timed_out = TRUE;
+  g_main_context_wakeup (NULL);
 
   return G_SOURCE_REMOVE;
 }
@@ -664,96 +683,16 @@ static GActionEntry exported_entries[] = {
 };
 
 static void
-list_cb (GObject      *source,
-         GAsyncResult *res,
-         gpointer      user_data)
-{
-  GDBusConnection *bus = G_DBUS_CONNECTION (source);
-  GMainLoop *loop = user_data;
-  GError *error = NULL;
-  GVariant *v;
-  gchar **actions;
-
-  v = g_dbus_connection_call_finish (bus, res, &error);
-  g_assert_nonnull (v);
-  g_variant_get (v, "(^a&s)", &actions);
-  g_assert_cmpint (g_strv_length (actions), ==, G_N_ELEMENTS (exported_entries));
-  g_free (actions);
-  g_variant_unref (v);
-  g_main_loop_quit (loop);
-}
-
-static gboolean
-call_list (gpointer user_data)
-{
-  GDBusConnection *bus;
-
-  bus = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, NULL);
-  g_dbus_connection_call (bus,
-                          g_dbus_connection_get_unique_name (bus),
-                          "/",
-                          "org.gtk.Actions",
-                          "List",
-                          NULL,
-                          NULL,
-                          0,
-                          G_MAXINT,
-                          NULL,
-                          list_cb,
-                          user_data);
-  g_object_unref (bus);
-
-  return G_SOURCE_REMOVE;
-}
-
-static void
-describe_cb (GObject      *source,
-             GAsyncResult *res,
-             gpointer      user_data)
-{
-  GDBusConnection *bus = G_DBUS_CONNECTION (source);
-  GMainLoop *loop = user_data;
-  GError *error = NULL;
-  GVariant *v;
-  gboolean enabled;
-  gchar *param;
-  GVariantIter *iter;
-
-  v = g_dbus_connection_call_finish (bus, res, &error);
-  g_assert_nonnull (v);
-  /* FIXME: there's an extra level of tuplelization in here */
-  g_variant_get (v, "((bgav))", &enabled, &param, &iter);
-  g_assert_true (enabled);
-  g_assert_cmpstr (param, ==, "");
-  g_assert_cmpint (g_variant_iter_n_children (iter), ==, 0);
-  g_free (param);
-  g_variant_iter_free (iter);
-  g_variant_unref (v);
-
-  g_main_loop_quit (loop);
-}
-
-static gboolean
-call_describe (gpointer user_data)
+async_result_cb (GObject      *source,
+                 GAsyncResult *res,
+                 gpointer      user_data)
 {
-  GDBusConnection *bus;
+  GAsyncResult **result_out = user_data;
 
-  bus = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, NULL);
-  g_dbus_connection_call (bus,
-                          g_dbus_connection_get_unique_name (bus),
-                          "/",
-                          "org.gtk.Actions",
-                          "Describe",
-                          g_variant_new ("(s)", "copy"),
-                          NULL,
-                          0,
-                          G_MAXINT,
-                          NULL,
-                          describe_cb,
-                          user_data);
-  g_object_unref (bus);
+  g_assert_null (*result_out);
+  *result_out = g_object_ref (res);
 
-  return G_SOURCE_REMOVE;
+  g_main_context_wakeup (NULL);
 }
 
 G_GNUC_BEGIN_IGNORE_DEPRECATIONS
@@ -800,15 +739,16 @@ test_dbus_export (void)
   GSimpleActionGroup *group;
   GDBusActionGroup *proxy;
   GSimpleAction *action;
-  GMainLoop *loop;
   GError *error = NULL;
   GVariant *v;
   guint id;
   gchar **actions;
   guint n_actions_added = 0, n_actions_enabled_changed = 0, n_actions_removed = 0, n_actions_state_changed = 0;
   gulong added_signal_id, enabled_changed_signal_id, removed_signal_id, state_changed_signal_id;
-
-  loop = g_main_loop_new (NULL, FALSE);
+  gboolean enabled;
+  gchar *param;
+  GVariantIter *iter;
+  GAsyncResult *async_result = NULL;
 
   session_bus_up ();
   bus = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, NULL);
@@ -842,16 +782,244 @@ test_dbus_export (void)
   g_strfreev (actions);
 
   /* check that calling "List" works too */
-  g_idle_add (call_list, loop);
-  g_main_loop_run (loop);
+  g_dbus_connection_call (bus,
+                          g_dbus_connection_get_unique_name (bus),
+                          "/",
+                          "org.gtk.Actions",
+                          "List",
+                          NULL,
+                          NULL,
+                          0,
+                          G_MAXINT,
+                          NULL,
+                          async_result_cb,
+                          &async_result);
+
+  while (async_result == NULL)
+    g_main_context_iteration (NULL, TRUE);
+
+  v = g_dbus_connection_call_finish (bus, async_result, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (v);
+  g_variant_get (v, "(^a&s)", &actions);
+  g_assert_cmpuint (g_strv_length (actions), ==, G_N_ELEMENTS (exported_entries));
+  g_free (actions);
+  g_variant_unref (v);
+  g_clear_object (&async_result);
 
   /* check that calling "Describe" works */
-  g_idle_add (call_describe, loop);
-  g_main_loop_run (loop);
+  g_dbus_connection_call (bus,
+                          g_dbus_connection_get_unique_name (bus),
+                          "/",
+                          "org.gtk.Actions",
+                          "Describe",
+                          g_variant_new ("(s)", "copy"),
+                          NULL,
+                          0,
+                          G_MAXINT,
+                          NULL,
+                          async_result_cb,
+                          &async_result);
+
+  while (async_result == NULL)
+    g_main_context_iteration (NULL, TRUE);
+
+  v = g_dbus_connection_call_finish (bus, async_result, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (v);
+  /* FIXME: there's an extra level of tuplelization in here */
+  g_variant_get (v, "((bgav))", &enabled, &param, &iter);
+  g_assert_true (enabled);
+  g_assert_cmpstr (param, ==, "");
+  g_assert_cmpint (g_variant_iter_n_children (iter), ==, 0);
+  g_free (param);
+  g_variant_iter_free (iter);
+  g_variant_unref (v);
+  g_clear_object (&async_result);
+
+  /* check that activating a parameterless action over D-Bus works */
+  g_assert_cmpint (activation_count ("undo"), ==, 0);
+
+  g_dbus_connection_call (bus,
+                          g_dbus_connection_get_unique_name (bus),
+                          "/",
+                          "org.gtk.Actions",
+                          "Activate",
+                          g_variant_new ("(sava{sv})", "undo", NULL, NULL),
+                          NULL,
+                          0,
+                          G_MAXINT,
+                          NULL,
+                          async_result_cb,
+                          &async_result);
+
+  while (async_result == NULL)
+    g_main_context_iteration (NULL, TRUE);
+
+  v = g_dbus_connection_call_finish (bus, async_result, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (v);
+  g_assert_true (g_variant_is_of_type (v, G_VARIANT_TYPE_UNIT));
+  g_variant_unref (v);
+  g_clear_object (&async_result);
+
+  g_assert_cmpint (activation_count ("undo"), ==, 1);
+
+  /* check that activating a parameterful action over D-Bus works */
+  g_assert_cmpint (activation_count ("lang"), ==, 0);
+  ensure_state (G_ACTION_GROUP (group), "lang", "'latin'");
+
+  g_dbus_connection_call (bus,
+                          g_dbus_connection_get_unique_name (bus),
+                          "/",
+                          "org.gtk.Actions",
+                          "Activate",
+                          g_variant_new ("(s@ava{sv})", "lang", g_variant_new_parsed ("[<'spanish'>]"), NULL),
+                          NULL,
+                          0,
+                          G_MAXINT,
+                          NULL,
+                          async_result_cb,
+                          &async_result);
+
+  while (async_result == NULL)
+    g_main_context_iteration (NULL, TRUE);
+
+  v = g_dbus_connection_call_finish (bus, async_result, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (v);
+  g_assert_true (g_variant_is_of_type (v, G_VARIANT_TYPE_UNIT));
+  g_variant_unref (v);
+  g_clear_object (&async_result);
+
+  g_assert_cmpint (activation_count ("lang"), ==, 1);
+  ensure_state (G_ACTION_GROUP (group), "lang", "'spanish'");
+
+  /* check that various error conditions are rejected */
+  {
+  struct
+    {
+      const gchar *action_name;
+      GVariant *parameter;  /* (owned floating) (nullable) */
+    }
+  activate_error_conditions[] =
+    {
+      { "nope", NULL },  /* non-existent action */
+      { "lang", g_variant_new_parsed ("[<@u 4>]") },  /* wrong parameter type */
+      { "lang", NULL },  /* parameter missing */
+      { "undo", g_variant_new_parsed ("[<'silly'>]") },  /* extraneous parameter */
+    };
+
+  for (gsize i = 0; i < G_N_ELEMENTS (activate_error_conditions); i++)
+    {
+      GVariant *parameter = g_steal_pointer (&activate_error_conditions[i].parameter);
+      const gchar *type_string = (parameter != NULL) ? "(s@ava{sv})" : "(sava{sv})";
+
+      g_dbus_connection_call (bus,
+                              g_dbus_connection_get_unique_name (bus),
+                              "/",
+                              "org.gtk.Actions",
+                              "Activate",
+                              g_variant_new (type_string,
+                                             activate_error_conditions[i].action_name,
+                                             g_steal_pointer (&parameter),
+                                             NULL),
+                              NULL,
+                              0,
+                              G_MAXINT,
+                              NULL,
+                              async_result_cb,
+                              &async_result);
+
+      while (async_result == NULL)
+        g_main_context_iteration (NULL, TRUE);
+
+      v = g_dbus_connection_call_finish (bus, async_result, &error);
+      g_assert_error (error, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS);
+      g_assert_null (v);
+      g_clear_error (&error);
+      g_clear_object (&async_result);
+    }
+  }
+
+  /* check that setting an action’s state over D-Bus works */
+  g_assert_cmpint (activation_count ("lang"), ==, 1);
+  ensure_state (G_ACTION_GROUP (group), "lang", "'spanish'");
+
+  g_dbus_connection_call (bus,
+                          g_dbus_connection_get_unique_name (bus),
+                          "/",
+                          "org.gtk.Actions",
+                          "SetState",
+                          g_variant_new ("(sva{sv})", "lang", g_variant_new_string ("portuguese"), NULL),
+                          NULL,
+                          0,
+                          G_MAXINT,
+                          NULL,
+                          async_result_cb,
+                          &async_result);
+
+  while (async_result == NULL)
+    g_main_context_iteration (NULL, TRUE);
+
+  v = g_dbus_connection_call_finish (bus, async_result, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (v);
+  g_assert_true (g_variant_is_of_type (v, G_VARIANT_TYPE_UNIT));
+  g_variant_unref (v);
+  g_clear_object (&async_result);
+
+  g_assert_cmpint (activation_count ("lang"), ==, 1);
+  ensure_state (G_ACTION_GROUP (group), "lang", "'portuguese'");
+
+  /* check that various error conditions are rejected */
+  {
+  struct
+    {
+      const gchar *action_name;
+      GVariant *state;  /* (owned floating) (not nullable) */
+    }
+  set_state_error_conditions[] =
+    {
+      { "nope", g_variant_new_string ("hello") },  /* non-existent action */
+      { "undo", g_variant_new_string ("not stateful") },  /* not a stateful action */
+      { "lang", g_variant_new_uint32 (3) },  /* wrong state type */
+    };
+
+  for (gsize i = 0; i < G_N_ELEMENTS (set_state_error_conditions); i++)
+    {
+      g_dbus_connection_call (bus,
+                              g_dbus_connection_get_unique_name (bus),
+                              "/",
+                              "org.gtk.Actions",
+                              "SetState",
+                              g_variant_new ("(s@va{sv})",
+                                             set_state_error_conditions[i].action_name,
+                                             g_variant_new_variant (g_steal_pointer (&set_state_error_conditions[i].state)),
+                                             NULL),
+                              NULL,
+                              0,
+                              G_MAXINT,
+                              NULL,
+                              async_result_cb,
+                              &async_result);
+
+      while (async_result == NULL)
+        g_main_context_iteration (NULL, TRUE);
+
+      v = g_dbus_connection_call_finish (bus, async_result, &error);
+      g_assert_error (error, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS);
+      g_assert_null (v);
+      g_clear_error (&error);
+      g_clear_object (&async_result);
+    }
+  }
 
   /* test that the initial transfer works */
   g_assert_true (G_IS_DBUS_ACTION_GROUP (proxy));
-  g_assert_true (compare_action_groups (G_ACTION_GROUP (group), G_ACTION_GROUP (proxy)));
+  while (!compare_action_groups (G_ACTION_GROUP (group), G_ACTION_GROUP (proxy)))
+    g_main_context_iteration (NULL, TRUE);
+  n_actions_state_changed = 0;
 
   /* test that various changes get propagated from group to proxy */
   n_actions_added = 0;
@@ -931,7 +1099,6 @@ test_dbus_export (void)
   g_signal_handler_disconnect (proxy, state_changed_signal_id);
   g_object_unref (proxy);
   g_object_unref (group);
-  g_main_loop_unref (loop);
   g_object_unref (bus);
 
   session_bus_down ();
@@ -1016,9 +1183,7 @@ test_bug679509 (void)
 {
   GDBusConnection *bus;
   GDBusActionGroup *proxy;
-  GMainLoop *loop;
-
-  loop = g_main_loop_new (NULL, FALSE);
+  gboolean timed_out = FALSE;
 
   session_bus_up ();
   bus = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, NULL);
@@ -1027,10 +1192,10 @@ test_bug679509 (void)
   g_strfreev (g_action_group_list_actions (G_ACTION_GROUP (proxy)));
   g_object_unref (proxy);
 
-  g_timeout_add (100, stop_loop, loop);
-  g_main_loop_run (loop);
+  g_timeout_add (100, timeout_cb, &timed_out);
+  while (!timed_out)
+    g_main_context_iteration (NULL, TRUE);
 
-  g_main_loop_unref (loop);
   g_object_unref (bus);
 
   session_bus_down ();
@@ -1062,22 +1227,6 @@ verify_changed (const gchar *log_entry)
 }
 
 static void
-ensure_state (GSimpleActionGroup *group,
-              const gchar        *action_name,
-              const gchar        *expected)
-{
-  GVariant *value;
-  gchar *printed;
-
-  value = g_action_group_get_action_state (G_ACTION_GROUP (group), action_name);
-  printed = g_variant_print (value, TRUE);
-  g_variant_unref (value);
-
-  g_assert_cmpstr (printed, ==, expected);
-  g_free (printed);
-}
-
-static void
 test_property_actions (void)
 {
   GSimpleActionGroup *group;
@@ -1137,11 +1286,11 @@ test_property_actions (void)
   g_object_unref (client);
   g_object_unref (app);
 
-  ensure_state (group, "app-id", "'org.gtk.test'");
-  ensure_state (group, "keepalive", "uint32 0");
-  ensure_state (group, "tls", "false");
-  ensure_state (group, "disable-proxy", "false");
-  ensure_state (group, "type", "'stream'");
+  ensure_state (G_ACTION_GROUP (group), "app-id", "'org.gtk.test'");
+  ensure_state (G_ACTION_GROUP (group), "keepalive", "uint32 0");
+  ensure_state (G_ACTION_GROUP (group), "tls", "false");
+  ensure_state (G_ACTION_GROUP (group), "disable-proxy", "false");
+  ensure_state (G_ACTION_GROUP (group), "type", "'stream'");
 
   verify_changed (NULL);
 
@@ -1149,88 +1298,88 @@ test_property_actions (void)
   g_action_group_change_action_state (G_ACTION_GROUP (group), "app-id", g_variant_new ("s", "org.gtk.test2"));
   verify_changed ("app-id:'org.gtk.test2'");
   g_assert_cmpstr (g_application_get_application_id (app), ==, "org.gtk.test2");
-  ensure_state (group, "app-id", "'org.gtk.test2'");
+  ensure_state (G_ACTION_GROUP (group), "app-id", "'org.gtk.test2'");
 
   g_action_group_activate_action (G_ACTION_GROUP (group), "app-id", g_variant_new ("s", "org.gtk.test3"));
   verify_changed ("app-id:'org.gtk.test3'");
   g_assert_cmpstr (g_application_get_application_id (app), ==, "org.gtk.test3");
-  ensure_state (group, "app-id", "'org.gtk.test3'");
+  ensure_state (G_ACTION_GROUP (group), "app-id", "'org.gtk.test3'");
 
   g_application_set_application_id (app, "org.gtk.test");
   verify_changed ("app-id:'org.gtk.test'");
-  ensure_state (group, "app-id", "'org.gtk.test'");
+  ensure_state (G_ACTION_GROUP (group), "app-id", "'org.gtk.test'");
 
   /* uint tests */
   g_action_group_change_action_state (G_ACTION_GROUP (group), "keepalive", g_variant_new ("u", 1234));
   verify_changed ("keepalive:uint32 1234");
   g_assert_cmpuint (g_application_get_inactivity_timeout (app), ==, 1234);
-  ensure_state (group, "keepalive", "uint32 1234");
+  ensure_state (G_ACTION_GROUP (group), "keepalive", "uint32 1234");
 
   g_action_group_activate_action (G_ACTION_GROUP (group), "keepalive", g_variant_new ("u", 5678));
   verify_changed ("keepalive:uint32 5678");
   g_assert_cmpuint (g_application_get_inactivity_timeout (app), ==, 5678);
-  ensure_state (group, "keepalive", "uint32 5678");
+  ensure_state (G_ACTION_GROUP (group), "keepalive", "uint32 5678");
 
   g_application_set_inactivity_timeout (app, 0);
   verify_changed ("keepalive:uint32 0");
-  ensure_state (group, "keepalive", "uint32 0");
+  ensure_state (G_ACTION_GROUP (group), "keepalive", "uint32 0");
 
   /* bool tests */
   g_action_group_change_action_state (G_ACTION_GROUP (group), "tls", g_variant_new ("b", TRUE));
   verify_changed ("tls:true");
   g_assert_true (g_socket_client_get_tls (client));
-  ensure_state (group, "tls", "true");
+  ensure_state (G_ACTION_GROUP (group), "tls", "true");
 
   g_action_group_change_action_state (G_ACTION_GROUP (group), "disable-proxy", g_variant_new ("b", TRUE));
   verify_changed ("disable-proxy:true");
-  ensure_state (group, "disable-proxy", "true");
+  ensure_state (G_ACTION_GROUP (group), "disable-proxy", "true");
   g_assert_false (g_socket_client_get_enable_proxy (client));
 
   /* test toggle true->false */
   g_action_group_activate_action (G_ACTION_GROUP (group), "tls", NULL);
   verify_changed ("tls:false");
   g_assert_false (g_socket_client_get_tls (client));
-  ensure_state (group, "tls", "false");
+  ensure_state (G_ACTION_GROUP (group), "tls", "false");
 
   /* and now back false->true */
   g_action_group_activate_action (G_ACTION_GROUP (group), "tls", NULL);
   verify_changed ("tls:true");
   g_assert_true (g_socket_client_get_tls (client));
-  ensure_state (group, "tls", "true");
+  ensure_state (G_ACTION_GROUP (group), "tls", "true");
 
   g_socket_client_set_tls (client, FALSE);
   verify_changed ("tls:false");
-  ensure_state (group, "tls", "false");
+  ensure_state (G_ACTION_GROUP (group), "tls", "false");
 
   /* now do the same for the inverted action */
   g_action_group_activate_action (G_ACTION_GROUP (group), "disable-proxy", NULL);
   verify_changed ("disable-proxy:false");
   g_assert_true (g_socket_client_get_enable_proxy (client));
-  ensure_state (group, "disable-proxy", "false");
+  ensure_state (G_ACTION_GROUP (group), "disable-proxy", "false");
 
   g_action_group_activate_action (G_ACTION_GROUP (group), "disable-proxy", NULL);
   verify_changed ("disable-proxy:true");
   g_assert_false (g_socket_client_get_enable_proxy (client));
-  ensure_state (group, "disable-proxy", "true");
+  ensure_state (G_ACTION_GROUP (group), "disable-proxy", "true");
 
   g_socket_client_set_enable_proxy (client, TRUE);
   verify_changed ("disable-proxy:false");
-  ensure_state (group, "disable-proxy", "false");
+  ensure_state (G_ACTION_GROUP (group), "disable-proxy", "false");
 
   /* enum tests */
   g_action_group_change_action_state (G_ACTION_GROUP (group), "type", g_variant_new ("s", "datagram"));
   verify_changed ("type:'datagram'");
   g_assert_cmpint (g_socket_client_get_socket_type (client), ==, G_SOCKET_TYPE_DATAGRAM);
-  ensure_state (group, "type", "'datagram'");
+  ensure_state (G_ACTION_GROUP (group), "type", "'datagram'");
 
   g_action_group_activate_action (G_ACTION_GROUP (group), "type", g_variant_new ("s", "stream"));
   verify_changed ("type:'stream'");
   g_assert_cmpint (g_socket_client_get_socket_type (client), ==, G_SOCKET_TYPE_STREAM);
-  ensure_state (group, "type", "'stream'");
+  ensure_state (G_ACTION_GROUP (group), "type", "'stream'");
 
   g_socket_client_set_socket_type (client, G_SOCKET_TYPE_SEQPACKET);
   verify_changed ("type:'seqpacket'");
-  ensure_state (group, "type", "'seqpacket'");
+  ensure_state (G_ACTION_GROUP (group), "type", "'seqpacket'");
 
   /* Check some error cases... */
   g_test_expect_message ("GLib-GIO", G_LOG_LEVEL_CRITICAL, "*non-existent*");
diff --git a/gio/tests/application-command-line.c b/gio/tests/application-command-line.c
new file mode 100644
index 000000000..185d49f58
--- /dev/null
+++ b/gio/tests/application-command-line.c
@@ -0,0 +1,92 @@
+/*
+ * Copyright © 2022 Endless OS Foundation, LLC
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Philip Withnall <pwithnall@endlessos.org>
+ */
+
+#include <gio/gio.h>
+#include <locale.h>
+
+
+static void
+test_basic_properties (void)
+{
+  GApplicationCommandLine *cl = NULL;
+  const gchar * const arguments[] = { "arg1", "arg2", "arg3", NULL };
+  GVariantBuilder options_builder = G_VARIANT_BUILDER_INIT (G_VARIANT_TYPE_VARDICT);
+  GVariantBuilder platform_data_builder = G_VARIANT_BUILDER_INIT (G_VARIANT_TYPE_VARDICT);
+  gchar **argv = NULL;
+  int argc = 0;
+  GVariantDict *options_dict;
+  GVariant *platform_data;
+  GVariantDict *platform_data_dict = NULL;
+  gboolean is_remote;
+
+  /* Basic construction. */
+  g_variant_builder_add (&options_builder, "{sv}", "option1", g_variant_new_string ("value1"));
+  g_variant_builder_add (&options_builder, "{sv}", "option2", g_variant_new_string ("value2"));
+
+  g_variant_builder_add (&platform_data_builder, "{sv}", "data1", g_variant_new_string ("data-value1"));
+  g_variant_builder_add (&platform_data_builder, "{sv}", "data2", g_variant_new_string ("data-value2"));
+
+  cl = g_object_new (G_TYPE_APPLICATION_COMMAND_LINE,
+                     "arguments", g_variant_new_bytestring_array (arguments, -1),
+                     "options", g_variant_builder_end (&options_builder),
+                     "platform-data", g_variant_builder_end (&platform_data_builder),
+                     NULL);
+  g_assert_nonnull (cl);
+
+  /* Check the getters. */
+  argv = g_application_command_line_get_arguments (cl, &argc);
+  g_assert_cmpint (argc, ==, 3);
+  g_assert_cmpstrv (argv, arguments);
+  g_clear_pointer (&argv, g_strfreev);
+
+  options_dict = g_application_command_line_get_options_dict (cl);
+  g_assert_nonnull (options_dict);
+  g_assert_true (g_variant_dict_contains (options_dict, "option1"));
+  g_assert_true (g_variant_dict_contains (options_dict, "option2"));
+
+  g_assert_false (g_application_command_line_get_is_remote (cl));
+
+  platform_data = g_application_command_line_get_platform_data (cl);
+  g_assert_nonnull (platform_data);
+  platform_data_dict = g_variant_dict_new (platform_data);
+  g_assert_true (g_variant_dict_contains (platform_data_dict, "data1"));
+  g_assert_true (g_variant_dict_contains (platform_data_dict, "data2"));
+  g_variant_dict_unref (platform_data_dict);
+  g_variant_unref (platform_data);
+
+  /* And g_object_get(). */
+  g_object_get (cl, "is-remote", &is_remote, NULL);
+  g_assert_false (is_remote);
+
+  g_clear_object (&cl);
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  setlocale (LC_ALL, "");
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/application-command-line/basic-properties", test_basic_properties);
+
+  return g_test_run ();
+}
diff --git a/gio/tests/fdo-notification-backend.c b/gio/tests/fdo-notification-backend.c
new file mode 100644
index 000000000..aed9aab67
--- /dev/null
+++ b/gio/tests/fdo-notification-backend.c
@@ -0,0 +1,326 @@
+/*
+ * Copyright © 2022 Endless OS Foundation, LLC
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Philip Withnall <pwithnall@endlessos.org>
+ */
+
+#include <gio/gio.h>
+#include <locale.h>
+
+#include <gio/giomodule-priv.h>
+#include "gio/gnotificationbackend.h"
+
+
+static GNotificationBackend *
+construct_backend (GApplication **app_out)
+{
+  GApplication *app = NULL;
+  GType fdo_type = G_TYPE_INVALID;
+  GNotificationBackend *backend = NULL;
+  GError *local_error = NULL;
+
+  /* Construct the app first and withdraw a notification, to ensure that IO modules are loaded. */
+  app = g_application_new ("org.gtk.TestApplication", G_APPLICATION_DEFAULT_FLAGS);
+  g_application_register (app, NULL, &local_error);
+  g_assert_no_error (local_error);
+  g_application_withdraw_notification (app, "org.gtk.TestApplication.NonexistentNotification");
+
+  fdo_type = g_type_from_name ("GFdoNotificationBackend");
+  g_assert_cmpuint (fdo_type, !=, G_TYPE_INVALID);
+
+  /* Replicate the behaviour from g_notification_backend_new_default(), which is
+   * not exported publicly so can‘t be easily used in the test. */
+  backend = g_object_new (fdo_type, NULL);
+  backend->application = app;
+  backend->dbus_connection = g_application_get_dbus_connection (app);
+  if (backend->dbus_connection)
+    g_object_ref (backend->dbus_connection);
+
+  if (app_out != NULL)
+    *app_out = g_object_ref (app);
+
+  g_clear_object (&app);
+
+  return g_steal_pointer (&backend);
+}
+
+static void
+test_construction (void)
+{
+  GNotificationBackend *backend = NULL;
+  GApplication *app = NULL;
+  GTestDBus *bus = NULL;
+
+  g_test_message ("Test constructing a GFdoNotificationBackend");
+
+  /* Set up a test session bus and connection. */
+  bus = g_test_dbus_new (G_TEST_DBUS_NONE);
+  g_test_dbus_up (bus);
+
+  backend = construct_backend (&app);
+  g_assert_nonnull (backend);
+
+  g_application_quit (app);
+  g_clear_object (&app);
+  g_clear_object (&backend);
+
+  g_test_dbus_down (bus);
+  g_clear_object (&bus);
+}
+
+static void
+daemon_method_call_cb (GDBusConnection       *connection,
+                       const gchar           *sender,
+                       const gchar           *object_path,
+                       const gchar           *interface_name,
+                       const gchar           *method_name,
+                       GVariant              *parameters,
+                       GDBusMethodInvocation *invocation,
+                       gpointer               user_data)
+{
+  GDBusMethodInvocation **current_method_invocation_out = user_data;
+
+  g_assert_null (*current_method_invocation_out);
+  *current_method_invocation_out = g_steal_pointer (&invocation);
+
+  g_main_context_wakeup (NULL);
+}
+
+static void
+name_acquired_or_lost_cb (GDBusConnection *connection,
+                          const gchar     *name,
+                          gpointer         user_data)
+{
+  gboolean *name_acquired = user_data;
+
+  *name_acquired = !*name_acquired;
+
+  g_main_context_wakeup (NULL);
+}
+
+static void
+dbus_activate_action_cb (GSimpleAction *action,
+                         GVariant      *parameter,
+                         gpointer       user_data)
+{
+  guint *n_activations = user_data;
+
+  *n_activations = *n_activations + 1;
+  g_main_context_wakeup (NULL);
+}
+
+static void
+assert_send_notification (GNotificationBackend   *backend,
+                          GDBusMethodInvocation **current_method_invocation,
+                          guint32                 notify_id)
+{
+  GNotification *notification = NULL;
+
+  notification = g_notification_new ("Some Notification");
+  G_NOTIFICATION_BACKEND_GET_CLASS (backend)->send_notification (backend, "notification1", notification);
+  g_clear_object (&notification);
+
+  while (*current_method_invocation == NULL)
+    g_main_context_iteration (NULL, TRUE);
+
+  g_assert_cmpstr (g_dbus_method_invocation_get_interface_name (*current_method_invocation), ==, "org.freedesktop.Notifications");
+  g_assert_cmpstr (g_dbus_method_invocation_get_method_name (*current_method_invocation), ==, "Notify");
+  g_dbus_method_invocation_return_value (g_steal_pointer (current_method_invocation), g_variant_new ("(u)", notify_id));
+}
+
+static void
+assert_emit_action_invoked (GDBusConnection *daemon_connection,
+                            GVariant        *parameters)
+{
+  GError *local_error = NULL;
+
+  g_dbus_connection_emit_signal (daemon_connection,
+                                 NULL,
+                                 "/org/freedesktop/Notifications",
+                                 "org.freedesktop.Notifications",
+                                 "ActionInvoked",
+                                 parameters,
+                                 &local_error);
+  g_assert_no_error (local_error);
+}
+
+static void
+test_dbus_activate_action (void)
+{
+  /* Very trimmed down version of
+   * https://specifications.freedesktop.org/notification-spec/notification-spec-latest.html */
+  const GDBusArgInfo daemon_notify_in_app_name = { -1, "AppName", "s", NULL };
+  const GDBusArgInfo daemon_notify_in_replaces_id = { -1, "ReplacesId", "u", NULL };
+  const GDBusArgInfo daemon_notify_in_app_icon = { -1, "AppIcon", "s", NULL };
+  const GDBusArgInfo daemon_notify_in_summary = { -1, "Summary", "s", NULL };
+  const GDBusArgInfo daemon_notify_in_body = { -1, "Body", "s", NULL };
+  const GDBusArgInfo daemon_notify_in_actions = { -1, "Actions", "as", NULL };
+  const GDBusArgInfo daemon_notify_in_hints = { -1, "Hints", "a{sv}", NULL };
+  const GDBusArgInfo daemon_notify_in_expire_timeout = { -1, "ExpireTimeout", "i", NULL };
+  const GDBusArgInfo *daemon_notify_in_args[] =
+    {
+      &daemon_notify_in_app_name,
+      &daemon_notify_in_replaces_id,
+      &daemon_notify_in_app_icon,
+      &daemon_notify_in_summary,
+      &daemon_notify_in_body,
+      &daemon_notify_in_actions,
+      &daemon_notify_in_hints,
+      &daemon_notify_in_expire_timeout,
+      NULL
+    };
+  const GDBusArgInfo daemon_notify_out_id = { -1, "Id", "u", NULL };
+  const GDBusArgInfo *daemon_notify_out_args[] = { &daemon_notify_out_id, NULL };
+  const GDBusMethodInfo daemon_notify_info = { -1, "Notify", (GDBusArgInfo **) daemon_notify_in_args, (GDBusArgInfo **) daemon_notify_out_args, NULL };
+  const GDBusMethodInfo *daemon_methods[] = { &daemon_notify_info, NULL };
+  const GDBusInterfaceInfo daemon_interface_info = { -1, "org.freedesktop.Notifications", (GDBusMethodInfo **) daemon_methods, NULL, NULL, NULL };
+
+  GTestDBus *bus = NULL;
+  GDBusConnection *daemon_connection = NULL;
+  guint daemon_object_id = 0, daemon_name_id = 0;
+  const GDBusInterfaceVTable vtable = { daemon_method_call_cb, NULL, NULL, { NULL, } };
+  GDBusMethodInvocation *current_method_invocation = NULL;
+  GApplication *app = NULL;
+  GNotificationBackend *backend = NULL;
+  guint32 notify_id;
+  GError *local_error = NULL;
+  const GActionEntry entries[] =
+    {
+      { "undo", dbus_activate_action_cb, NULL, NULL,      NULL, { 0 } },
+      { "lang", dbus_activate_action_cb, "s",  "'latin'", NULL, { 0 } },
+    };
+  guint n_activations = 0;
+  gboolean name_acquired = FALSE;
+
+  g_test_summary ("Test how the backend handles valid and invalid ActionInvoked signals from the daemon");
+
+  /* Set up a test session bus and connection. */
+  bus = g_test_dbus_new (G_TEST_DBUS_NONE);
+  g_test_dbus_up (bus);
+
+  /* Create a mock org.freedesktop.Notifications daemon */
+  daemon_connection = g_dbus_connection_new_for_address_sync (g_test_dbus_get_bus_address (bus),
+                                                              G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT |
+                                                              G_DBUS_CONNECTION_FLAGS_MESSAGE_BUS_CONNECTION,
+                                                              NULL, NULL, &local_error);
+  g_assert_no_error (local_error);
+
+  daemon_object_id = g_dbus_connection_register_object (daemon_connection,
+                                                        "/org/freedesktop/Notifications",
+                                                        (GDBusInterfaceInfo *) &daemon_interface_info,
+                                                        &vtable,
+                                                        &current_method_invocation, NULL, &local_error);
+  g_assert_no_error (local_error);
+
+  daemon_name_id = g_bus_own_name_on_connection (daemon_connection,
+                                                 "org.freedesktop.Notifications",
+                                                 G_BUS_NAME_OWNER_FLAGS_DO_NOT_QUEUE,
+                                                 name_acquired_or_lost_cb,
+                                                 name_acquired_or_lost_cb,
+                                                 &name_acquired, NULL);
+
+  while (!name_acquired)
+    g_main_context_iteration (NULL, TRUE);
+
+  /* Construct our FDO backend under test */
+  backend = construct_backend (&app);
+  g_action_map_add_action_entries (G_ACTION_MAP (app), entries, G_N_ELEMENTS (entries), &n_activations);
+
+  /* Send a notification to ensure that the backend is listening for D-Bus action signals. */
+  notify_id = 1233;
+  assert_send_notification (backend, &current_method_invocation, ++notify_id);
+
+  /* Send a valid fake action signal. */
+  n_activations = 0;
+  assert_emit_action_invoked (daemon_connection, g_variant_new ("(us)", notify_id, "app.undo"));
+
+  while (n_activations == 0)
+    g_main_context_iteration (NULL, TRUE);
+
+  g_assert_cmpuint (n_activations, ==, 1);
+
+  /* Send a valid fake action signal with a target. We have to create a new
+   * notification first, as invoking an action on a notification removes it, and
+   * the GLib implementation of org.freedesktop.Notifications doesn’t currently
+   * support the `resident` hint to avoid that. */
+  assert_send_notification (backend, &current_method_invocation, ++notify_id);
+  n_activations = 0;
+  assert_emit_action_invoked (daemon_connection, g_variant_new ("(us)", notify_id, "app.lang::spanish"));
+
+  while (n_activations == 0)
+    g_main_context_iteration (NULL, TRUE);
+
+  g_assert_cmpuint (n_activations, ==, 1);
+
+  /* Send a series of invalid action signals, followed by one valid one which
+   * we should be able to detect. */
+  assert_send_notification (backend, &current_method_invocation, ++notify_id);
+  n_activations = 0;
+  assert_emit_action_invoked (daemon_connection, g_variant_new ("(us)", notify_id, "app.nonexistent"));
+  assert_emit_action_invoked (daemon_connection, g_variant_new ("(us)", notify_id, "app.lang(13)"));
+  assert_emit_action_invoked (daemon_connection, g_variant_new ("(us)", notify_id, "app.undo::should-have-no-parameter"));
+  assert_emit_action_invoked (daemon_connection, g_variant_new ("(us)", notify_id, "app.lang"));
+  assert_emit_action_invoked (daemon_connection, g_variant_new ("(us)", notify_id, "undo"));  /* no `app.` prefix */
+  assert_emit_action_invoked (daemon_connection, g_variant_new ("(us)", notify_id, "app.lang("));  /* invalid parse format */
+  assert_emit_action_invoked (daemon_connection, g_variant_new ("(us)", notify_id, "app.undo"));
+
+  while (n_activations == 0)
+    g_main_context_iteration (NULL, TRUE);
+
+  g_assert_cmpuint (n_activations, ==, 1);
+
+  /* Shut down. */
+  g_assert_null (current_method_invocation);
+
+  g_application_quit (app);
+  g_clear_object (&app);
+  g_clear_object (&backend);
+
+  g_dbus_connection_unregister_object (daemon_connection, daemon_object_id);
+  g_bus_unown_name (daemon_name_id);
+
+  g_dbus_connection_flush_sync (daemon_connection, NULL, &local_error);
+  g_assert_no_error (local_error);
+  g_dbus_connection_close_sync (daemon_connection, NULL, &local_error);
+  g_assert_no_error (local_error);
+
+  g_clear_object (&daemon_connection);
+
+  g_test_dbus_down (bus);
+  g_clear_object (&bus);
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  setlocale (LC_ALL, "");
+
+  /* Force use of the FDO backend */
+  g_setenv ("GNOTIFICATION_BACKEND", "freedesktop", TRUE);
+
+  g_test_init (&argc, &argv, NULL);
+
+  /* Make sure we don’t send notifications to the actual D-Bus session. */
+  g_test_dbus_unset ();
+
+  g_test_add_func ("/fdo-notification-backend/construction", test_construction);
+  g_test_add_func ("/fdo-notification-backend/dbus/activate-action", test_dbus_activate_action);
+
+  return g_test_run ();
+}
diff --git a/gio/tests/gapplication.c b/gio/tests/gapplication.c
index bf0395cdb..4320352d1 100644
--- a/gio/tests/gapplication.c
+++ b/gio/tests/gapplication.c
@@ -1194,6 +1194,493 @@ test_replace (gconstpointer data)
     }
 }
 
+static void
+dbus_activate_cb (GApplication *app,
+                  gpointer      user_data)
+{
+  guint *n_activations = user_data;
+
+  *n_activations = *n_activations + 1;
+  g_main_context_wakeup (NULL);
+}
+
+static void dbus_startup_reply_cb (GObject      *source_object,
+                                   GAsyncResult *result,
+                                   gpointer      user_data);
+static gboolean dbus_startup_reply_idle_cb (gpointer user_data);
+
+static void
+dbus_startup_cb (GApplication *app,
+                 gpointer      user_data)
+{
+  GDBusConnection *connection = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, NULL);
+  GDBusMessage *message = G_DBUS_MESSAGE (user_data);
+
+  g_assert_nonnull (connection);
+
+  g_dbus_connection_send_message_with_reply (connection, message,
+                                             G_DBUS_SEND_MESSAGE_FLAGS_NONE, -1,
+                                             NULL, NULL,
+                                             dbus_startup_reply_cb, g_object_ref (app));
+
+  g_clear_object (&connection);
+}
+
+static void
+dbus_startup_reply_cb (GObject      *source_object,
+                       GAsyncResult *result,
+                       gpointer      user_data)
+{
+  GDBusConnection *connection = G_DBUS_CONNECTION (source_object);
+  GApplication *app = G_APPLICATION (user_data);
+  GDBusMessage *reply = NULL;
+  GError *local_error = NULL;
+
+  reply = g_dbus_connection_send_message_with_reply_finish (connection, result, &local_error);
+  g_assert_no_error (local_error);
+
+  /* Nothing to check on the reply for now. */
+  g_clear_object (&reply);
+
+  /* Release the app in an idle callback, so there’s time to process other
+   * pending sources first. */
+  g_idle_add_full (G_PRIORITY_LOW, dbus_startup_reply_idle_cb, g_steal_pointer (&app), g_object_unref);
+}
+
+static gboolean
+dbus_startup_reply_idle_cb (gpointer user_data)
+{
+  GApplication *app = G_APPLICATION (user_data);
+
+  g_application_release (app);
+
+  return G_SOURCE_REMOVE;
+}
+
+static void
+test_dbus_activate (void)
+{
+  GTestDBus *bus = NULL;
+  GVariantBuilder builder;
+  GDBusMessage *message = NULL;
+  GPtrArray *messages = NULL;  /* (element-type GDBusMessage) (owned) */
+  gsize i;
+
+  g_test_summary ("Test that calling the Activate D-Bus method works");
+
+  /* Try various different messages */
+  messages = g_ptr_array_new_with_free_func (g_object_unref);
+
+  /* Via org.gtk.Application */
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.Activate",
+                                            "/org/gtk/TestApplication/Activate",
+                                            "org.gtk.Application",
+                                            "Activate");
+  g_dbus_message_set_body (message, g_variant_new ("(a{sv})", NULL));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* Via org.freedesktop.Application */
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.Activate",
+                                            "/org/gtk/TestApplication/Activate",
+                                            "org.freedesktop.Application",
+                                            "Activate");
+  g_dbus_message_set_body (message, g_variant_new ("(a{sv})", NULL));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* With some platform data */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("a{sv}"));
+  g_variant_builder_add (&builder, "{sv}", "cwd", g_variant_new_bytestring ("/home/henry"));
+
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.Activate",
+                                            "/org/gtk/TestApplication/Activate",
+                                            "org.gtk.Application",
+                                            "Activate");
+  g_dbus_message_set_body (message, g_variant_new ("(a{sv})", &builder));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* Try each message */
+  bus = g_test_dbus_new (G_TEST_DBUS_NONE);
+  g_test_dbus_up (bus);
+
+  for (i = 0; i < messages->len; i++)
+    {
+      GApplication *app = NULL;
+      gulong activate_id, startup_id;
+      guint n_activations = 0;
+
+      g_test_message ("Message %" G_GSIZE_FORMAT, i);
+
+      app = g_application_new ("org.gtk.TestApplication.Activate", G_APPLICATION_DEFAULT_FLAGS);
+      activate_id = g_signal_connect (app, "activate", G_CALLBACK (dbus_activate_cb), &n_activations);
+      startup_id = g_signal_connect (app, "startup", G_CALLBACK (dbus_startup_cb), messages->pdata[i]);
+
+      g_application_hold (app);
+      g_application_run (app, 0, NULL);
+
+      /* It’ll be activated once as normal, and once due to the D-Bus call */
+      g_assert_cmpuint (n_activations, ==, 2);
+
+      g_signal_handler_disconnect (app, startup_id);
+      g_signal_handler_disconnect (app, activate_id);
+      g_clear_object (&app);
+    }
+
+  g_ptr_array_unref (messages);
+
+  g_test_dbus_down (bus);
+  g_clear_object (&bus);
+}
+
+static void
+dbus_activate_noop_cb (GApplication *app,
+                       gpointer      user_data)
+{
+  /* noop */
+}
+
+static void
+dbus_open_cb (GApplication *app,
+              gpointer      files,
+              int           n_files,
+              char         *hint,
+              gpointer      user_data)
+{
+  guint *n_opens = user_data;
+
+  *n_opens = *n_opens + 1;
+  g_main_context_wakeup (NULL);
+}
+
+static void
+test_dbus_open (void)
+{
+  GTestDBus *bus = NULL;
+  GVariantBuilder builder, builder2;
+  GDBusMessage *message = NULL;
+  GPtrArray *messages = NULL;  /* (element-type GDBusMessage) (owned) */
+  gsize i;
+
+  g_test_summary ("Test that calling the Open D-Bus method works");
+
+  /* Try various different messages */
+  messages = g_ptr_array_new_with_free_func (g_object_unref);
+
+  /* Via org.gtk.Application */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("as"));
+  g_variant_builder_add (&builder, "s", "file:///home/henry/test");
+
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.Open",
+                                            "/org/gtk/TestApplication/Open",
+                                            "org.gtk.Application",
+                                            "Open");
+  g_dbus_message_set_body (message, g_variant_new ("(assa{sv})", &builder, "hint", NULL));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* Via org.freedesktop.Application (which has no hint parameter) */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("as"));
+  g_variant_builder_add (&builder, "s", "file:///home/henry/test");
+
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.Open",
+                                            "/org/gtk/TestApplication/Open",
+                                            "org.freedesktop.Application",
+                                            "Open");
+  g_dbus_message_set_body (message, g_variant_new ("(asa{sv})", &builder, NULL));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* With some platform data and more than one file */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("as"));
+  g_variant_builder_add (&builder, "s", "file:///home/henry/test");
+  g_variant_builder_add (&builder, "s", "file:///home/henry/test2");
+
+  g_variant_builder_init (&builder2, G_VARIANT_TYPE ("a{sv}"));
+  g_variant_builder_add (&builder2, "{sv}", "cwd", g_variant_new_bytestring ("/home/henry"));
+
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.Open",
+                                            "/org/gtk/TestApplication/Open",
+                                            "org.gtk.Application",
+                                            "Open");
+  g_dbus_message_set_body (message, g_variant_new ("(assa{sv})", &builder, "", &builder2));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* No files */
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.Open",
+                                            "/org/gtk/TestApplication/Open",
+                                            "org.gtk.Application",
+                                            "Open");
+  g_dbus_message_set_body (message, g_variant_new ("(assa{sv})", NULL, "", NULL));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* Try each message */
+  bus = g_test_dbus_new (G_TEST_DBUS_NONE);
+  g_test_dbus_up (bus);
+
+  for (i = 0; i < messages->len; i++)
+    {
+      GApplication *app = NULL;
+      gulong activate_id, open_id, startup_id;
+      guint n_opens = 0;
+
+      g_test_message ("Message %" G_GSIZE_FORMAT, i);
+
+      app = g_application_new ("org.gtk.TestApplication.Open", G_APPLICATION_HANDLES_OPEN);
+      activate_id = g_signal_connect (app, "activate", G_CALLBACK (dbus_activate_noop_cb), NULL);
+      open_id = g_signal_connect (app, "open", G_CALLBACK (dbus_open_cb), &n_opens);
+      startup_id = g_signal_connect (app, "startup", G_CALLBACK (dbus_startup_cb), messages->pdata[i]);
+
+      g_application_hold (app);
+      g_application_run (app, 0, NULL);
+
+      g_assert_cmpuint (n_opens, ==, 1);
+
+      g_signal_handler_disconnect (app, startup_id);
+      g_signal_handler_disconnect (app, open_id);
+      g_signal_handler_disconnect (app, activate_id);
+      g_clear_object (&app);
+    }
+
+  g_ptr_array_unref (messages);
+
+  g_test_dbus_down (bus);
+  g_clear_object (&bus);
+}
+
+static void
+dbus_command_line_cb (GApplication            *app,
+                      GApplicationCommandLine *command_line,
+                      gpointer                 user_data)
+{
+  guint *n_command_lines = user_data;
+
+  *n_command_lines = *n_command_lines + 1;
+  g_main_context_wakeup (NULL);
+}
+
+static void
+test_dbus_command_line (void)
+{
+  GTestDBus *bus = NULL;
+  GVariantBuilder builder, builder2;
+  GDBusMessage *message = NULL;
+  GPtrArray *messages = NULL;  /* (element-type GDBusMessage) (owned) */
+  gsize i;
+
+  g_test_summary ("Test that calling the CommandLine D-Bus method works");
+
+  /* Try various different messages */
+  messages = g_ptr_array_new_with_free_func (g_object_unref);
+
+  /* Via org.gtk.Application */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("aay"));
+  g_variant_builder_add (&builder, "^ay", "test-program");
+  g_variant_builder_add (&builder, "^ay", "--open");
+  g_variant_builder_add (&builder, "^ay", "/path/to/something");
+
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.CommandLine",
+                                            "/org/gtk/TestApplication/CommandLine",
+                                            "org.gtk.Application",
+                                            "CommandLine");
+  g_dbus_message_set_body (message, g_variant_new ("(oaaya{sv})",
+                                                   "/my/org/gtk/private/CommandLine",
+                                                   &builder, NULL));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* With platform data */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("aay"));
+  g_variant_builder_add (&builder, "^ay", "test-program");
+  g_variant_builder_add (&builder, "^ay", "--open");
+  g_variant_builder_add (&builder, "^ay", "/path/to/something");
+
+  g_variant_builder_init (&builder2, G_VARIANT_TYPE ("a{sv}"));
+  g_variant_builder_add (&builder2, "{sv}", "cwd", g_variant_new_bytestring ("/home"));
+  g_variant_builder_add_parsed (&builder2, "{'environ', <@aay [ b'HOME=/home/bloop', b'PATH=/blah']>}");
+  g_variant_builder_add_parsed (&builder2, "{'options', <{'a': <@u 32>, 'b': <'bloop'>}>}");
+
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.CommandLine",
+                                            "/org/gtk/TestApplication/CommandLine",
+                                            "org.gtk.Application",
+                                            "CommandLine");
+  g_dbus_message_set_body (message, g_variant_new ("(oaaya{sv})",
+                                                   "/my/org/gtk/private/CommandLine",
+                                                   &builder, &builder2));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* With invalid typed platform data */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("aay"));
+  g_variant_builder_add (&builder, "^ay", "test-program");
+  g_variant_builder_add (&builder, "^ay", "--open");
+  g_variant_builder_add (&builder, "^ay", "/path/to/something");
+
+  g_variant_builder_init (&builder2, G_VARIANT_TYPE ("a{sv}"));
+  g_variant_builder_add (&builder2, "{sv}", "cwd", g_variant_new_string ("/home should be a bytestring"));
+  g_variant_builder_add_parsed (&builder2, "{'environ', <['HOME=should be a bytestring', 'PATH=this also']>}");
+  g_variant_builder_add_parsed (&builder2, "{'options', <['should be a', 'dict']>}");
+
+  message = g_dbus_message_new_method_call ("org.gtk.TestApplication.CommandLine",
+                                            "/org/gtk/TestApplication/CommandLine",
+                                            "org.gtk.Application",
+                                            "CommandLine");
+  g_dbus_message_set_body (message, g_variant_new ("(oaaya{sv})",
+                                                   "/my/org/gtk/private/CommandLine",
+                                                   &builder, &builder2));
+  g_ptr_array_add (messages, g_steal_pointer (&message));
+
+  /* Try each message */
+  bus = g_test_dbus_new (G_TEST_DBUS_NONE);
+  g_test_dbus_up (bus);
+
+  for (i = 0; i < messages->len; i++)
+    {
+      GApplication *app = NULL;
+      gulong activate_id, command_line_id, startup_id;
+      guint n_command_lines = 0;
+
+      g_test_message ("Message %" G_GSIZE_FORMAT, i);
+
+      app = g_application_new ("org.gtk.TestApplication.CommandLine", G_APPLICATION_HANDLES_COMMAND_LINE);
+      activate_id = g_signal_connect (app, "activate", G_CALLBACK (dbus_activate_noop_cb), NULL);
+      command_line_id = g_signal_connect (app, "command-line", G_CALLBACK (dbus_command_line_cb), &n_command_lines);
+      startup_id = g_signal_connect (app, "startup", G_CALLBACK (dbus_startup_cb), messages->pdata[i]);
+
+      g_application_hold (app);
+      g_application_run (app, 0, NULL);
+
+      /* It’s called once for handling the local command line on startup, and again
+       * for the D-Bus call */
+      g_assert_cmpuint (n_command_lines, ==, 2);
+
+      g_signal_handler_disconnect (app, startup_id);
+      g_signal_handler_disconnect (app, command_line_id);
+      g_signal_handler_disconnect (app, activate_id);
+      g_clear_object (&app);
+    }
+
+  g_ptr_array_unref (messages);
+
+  g_test_dbus_down (bus);
+  g_clear_object (&bus);
+}
+
+static void
+dbus_activate_action_cb (GSimpleAction *action,
+                         GVariant      *parameter,
+                         gpointer       user_data)
+{
+  guint *n_activations = user_data;
+
+  *n_activations = *n_activations + 1;
+  g_main_context_wakeup (NULL);
+}
+
+static void
+test_dbus_activate_action (void)
+{
+  GTestDBus *bus = NULL;
+  GVariantBuilder builder;
+  struct
+    {
+      GDBusMessage *message;  /* (not nullable) (owned) */
+      guint n_expected_activations;
+    } messages[6];
+  gsize i;
+
+  g_test_summary ("Test that calling the ActivateAction D-Bus method works");
+
+  /* Action without parameter */
+  messages[0].message = g_dbus_message_new_method_call ("org.gtk.TestApplication.ActivateAction",
+                                                        "/org/gtk/TestApplication/ActivateAction",
+                                                        "org.freedesktop.Application",
+                                                        "ActivateAction");
+  g_dbus_message_set_body (messages[0].message, g_variant_new ("(sava{sv})", "undo", NULL, NULL));
+  messages[0].n_expected_activations = 1;
+
+  /* Action with parameter */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("av"));
+  g_variant_builder_add (&builder, "v", g_variant_new_string ("spanish"));
+
+  messages[1].message = g_dbus_message_new_method_call ("org.gtk.TestApplication.ActivateAction",
+                                                        "/org/gtk/TestApplication/ActivateAction",
+                                                        "org.freedesktop.Application",
+                                                        "ActivateAction");
+  g_dbus_message_set_body (messages[1].message, g_variant_new ("(sava{sv})", "lang", &builder, NULL));
+  messages[1].n_expected_activations = 1;
+
+  /* Action with unexpected parameter */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("av"));
+  g_variant_builder_add (&builder, "v", g_variant_new_string ("should not be passed"));
+
+  messages[2].message = g_dbus_message_new_method_call ("org.gtk.TestApplication.ActivateAction",
+                                                        "/org/gtk/TestApplication/ActivateAction",
+                                                        "org.freedesktop.Application",
+                                                        "ActivateAction");
+  g_dbus_message_set_body (messages[2].message, g_variant_new ("(sava{sv})", "undo", &builder, NULL));
+  messages[2].n_expected_activations = 0;
+
+  /* Action without required parameter */
+  messages[3].message = g_dbus_message_new_method_call ("org.gtk.TestApplication.ActivateAction",
+                                                        "/org/gtk/TestApplication/ActivateAction",
+                                                        "org.freedesktop.Application",
+                                                        "ActivateAction");
+  g_dbus_message_set_body (messages[3].message, g_variant_new ("(sava{sv})", "lang", NULL, NULL));
+  messages[3].n_expected_activations = 0;
+
+  /* Action with wrong parameter type */
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("av"));
+  g_variant_builder_add (&builder, "v", g_variant_new_uint32 (42));
+
+  messages[4].message = g_dbus_message_new_method_call ("org.gtk.TestApplication.ActivateAction",
+                                                        "/org/gtk/TestApplication/ActivateAction",
+                                                        "org.freedesktop.Application",
+                                                        "ActivateAction");
+  g_dbus_message_set_body (messages[4].message, g_variant_new ("(sava{sv})", "lang", &builder, NULL));
+  messages[4].n_expected_activations = 0;
+
+  /* Nonexistent action */
+  messages[5].message = g_dbus_message_new_method_call ("org.gtk.TestApplication.ActivateAction",
+                                                        "/org/gtk/TestApplication/ActivateAction",
+                                                        "org.freedesktop.Application",
+                                                        "ActivateAction");
+  g_dbus_message_set_body (messages[5].message, g_variant_new ("(sava{sv})", "nonexistent", NULL, NULL));
+  messages[5].n_expected_activations = 0;
+
+  /* Try each message */
+  bus = g_test_dbus_new (G_TEST_DBUS_NONE);
+  g_test_dbus_up (bus);
+
+  for (i = 0; i < G_N_ELEMENTS (messages); i++)
+    {
+      GApplication *app = NULL;
+      gulong activate_id, startup_id;
+      const GActionEntry entries[] =
+        {
+          { "undo", dbus_activate_action_cb, NULL, NULL,      NULL, { 0 } },
+          { "lang", dbus_activate_action_cb,  "s",  "'latin'", NULL, { 0 } },
+        };
+      guint n_activations = 0;
+
+      g_test_message ("Message %" G_GSIZE_FORMAT, i);
+
+      app = g_application_new ("org.gtk.TestApplication.ActivateAction", G_APPLICATION_DEFAULT_FLAGS);
+      activate_id = g_signal_connect (app, "activate", G_CALLBACK (dbus_activate_noop_cb), NULL);
+      startup_id = g_signal_connect (app, "startup", G_CALLBACK (dbus_startup_cb), messages[i].message);
+
+      /* Export some actions. */
+      g_action_map_add_action_entries (G_ACTION_MAP (app), entries, G_N_ELEMENTS (entries), &n_activations);
+
+      g_application_hold (app);
+      g_application_run (app, 0, NULL);
+
+      g_assert_cmpuint (n_activations, ==, messages[i].n_expected_activations);
+
+      g_signal_handler_disconnect (app, startup_id);
+      g_signal_handler_disconnect (app, activate_id);
+      g_clear_object (&app);
+      g_clear_object (&messages[i].message);
+    }
+
+  g_test_dbus_down (bus);
+  g_clear_object (&bus);
+}
+
 int
 main (int argc, char **argv)
 {
@@ -1225,6 +1712,10 @@ main (int argc, char **argv)
   g_test_add_func ("/gapplication/api", test_api);
   g_test_add_data_func ("/gapplication/replace", GINT_TO_POINTER (TRUE), test_replace);
   g_test_add_data_func ("/gapplication/no-replace", GINT_TO_POINTER (FALSE), test_replace);
+  g_test_add_func ("/gapplication/dbus/activate", test_dbus_activate);
+  g_test_add_func ("/gapplication/dbus/open", test_dbus_open);
+  g_test_add_func ("/gapplication/dbus/command-line", test_dbus_command_line);
+  g_test_add_func ("/gapplication/dbus/activate-action", test_dbus_activate_action);
 
   return g_test_run ();
 }
diff --git a/gio/tests/meson.build b/gio/tests/meson.build
index e7fa812c4..41d4e3e6c 100644
--- a/gio/tests/meson.build
+++ b/gio/tests/meson.build
@@ -44,6 +44,7 @@ giotypefuncs_inc = custom_target(
 
 #  Test programs buildable on all platforms
 gio_tests = {
+  'application-command-line': {},
   'appmonitor' : {
     # FIXME: https://gitlab.gnome.org/GNOME/glib/-/issues/1392
     'should_fail' : host_system == 'darwin',
@@ -350,6 +351,7 @@ if host_machine.system() != 'windows'
         'extra_sources' : extra_sources,
         'suite' : ['slow'],
       },
+      'fdo-notification-backend': {},
       'gdbus-auth' : {'extra_sources' : extra_sources},
       'gdbus-bz627724' : {'extra_sources' : extra_sources},
       'gdbus-close-pending' : {'extra_sources' : extra_sources},