diff --git a/tests/runtests.py b/tests/runtests.py
index 14014f4b01..4956832a5b 100755
--- a/tests/runtests.py
+++ b/tests/runtests.py
@@ -143,6 +143,7 @@ def setup(verbosity, test_labels):
             bits = bits[:1]
         test_labels_set.add('.'.join(bits))
 
+    installed_app_names = set(get_installed())
     for modpath, module_name in test_modules:
         if modpath:
             module_label = '.'.join([modpath, module_name])
@@ -159,16 +160,12 @@ def setup(verbosity, test_labels):
                 module_label == label or module_label.startswith(label + '.')
                 for label in test_labels_set)
 
-        installed_app_names = set(get_installed())
         if module_found_in_labels and module_label not in installed_app_names:
             if verbosity >= 2:
                 print("Importing application %s" % module_name)
-            # HACK.
             settings.INSTALLED_APPS.append(module_label)
-            app_config = AppConfig.create(module_label)
-            apps.app_configs[app_config.label] = app_config
-            app_config.import_models(apps.all_models[app_config.label])
-            apps.clear_cache()
+
+    apps.set_installed_apps(settings.INSTALLED_APPS)
 
     return state