TEST_MODE always exists now, so check its value, don't rely on its existence to know that we're in test mode.

core/config/config.php

@@ -122,7 +122,7 @@ $config['modules'] = array(
   THEMEPATH . 'admin_default'
 );
 
-if (defined('TEST_MODE')) {
+if (TEST_MODE) {
   array_splice($config['modules'], 0, 0,
                array(MODPATH . 'gallery_unit_test',
                      MODPATH . 'unit_test'));

modules/gallery_unit_test/controllers/gallery_unit_test.php

@@ -19,7 +19,7 @@
  */
 class Gallery_Unit_Test_Controller extends Controller {
   function Index() {
-    if (!defined('TEST_MODE')) {
+    if (!TEST_MODE) {
       print Kohana::show_404();
     }