tests/wayland: Add test for buffer transforms

Ensure that buffer transforms are correctly rendered.

This test would fail without the commit
"wayland/surface: Swap 90 and 270 degree transforms"

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1055>

src/tests/wayland-test-clients/meson.build

@@ -46,6 +46,9 @@ common_sources = [
 ]
 
 wayland_test_clients = [
+  {
+    'name': 'buffer-transform',
+  },
   {
     'name': 'subsurface-remap-toplevel',
   },

src/tests/wayland-unit-tests.c

@@ -65,6 +65,16 @@ subsurface_remap_toplevel (void)
   meta_wayland_test_client_finish (wayland_test_client);
 }
 
+static void
+buffer_transform (void)
+{
+  MetaWaylandTestClient *wayland_test_client;
+
+  wayland_test_client =
+    meta_wayland_test_client_new ("buffer-transform");
+  meta_wayland_test_client_finish (wayland_test_client);
+}
+
 static void
 subsurface_reparenting (void)
 {
@@ -656,6 +666,8 @@ on_after_tests (void)
 static void
 init_tests (void)
 {
+  g_test_add_func ("/wayland/buffer/transform",
+                   buffer_transform);
   g_test_add_func ("/wayland/subsurface/remap-toplevel",
                    subsurface_remap_toplevel);
   g_test_add_func ("/wayland/subsurface/reparent",