Update test

jupyterlab/tests/test_jupyterlab.py

@@ -121,7 +121,7 @@ class TestExtension(TestCase):
         path = pjoin(commands.get_app_dir(), 'extensions', '*python-tests*.tgz')
         install_extension(self.source_dir)
         assert glob.glob(path)
-        assert '@jupyterlab/python-tests' in list_extensions()
+        assert '@jupyterlab/python-tests' in _get_extensions(self.app_dir)
 
     def test_install_failed(self):
         path = os.path.realpath(pjoin(here, '..'))