[gtk+] Expand visual tests a bit

[Matthias Clasen <matthiasc src gnome org>]

commit 669336cf95771ccb5852b57d15c76ff43a8788a4
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Mar 28 19:28:57 2016 -0400

    Expand visual tests a bit

 testsuite/gdk/visual.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/testsuite/gdk/visual.c b/testsuite/gdk/visual.c
index ad905fa..b8c6ab2 100644
--- a/testsuite/gdk/visual.c
+++ b/testsuite/gdk/visual.c
@@ -75,6 +75,9 @@ test_list_visuals (void)
         found_system = TRUE;
       if (visual == rgba_visual)
         found_rgba = TRUE;
+      g_assert_true (GDK_IS_VISUAL (visual));
+
+      g_assert_true (gdk_visual_get_screen (visual) == screen);
     }
   g_list_free (list);