text: from toga_dummy.utils import TestCase
  from toga_winforms import window
  
  
  class TestWindow(TestCase):
      def setUp(self):
          super().setUp()
          self.window = window.Window
  
      def test_build_filter(self):
          test_filter = self.window.build_filter(None, ["txt"])
          self.assertEqual(test_filter, "txt files (*.txt)|*.txt|All files (*.*)|*.*")
  