add test without mock

sdks/python/apache_beam/transforms/fully_qualified_named_transform_test.py

@@ -120,13 +120,29 @@ def test_glob_filter(self):
         FullyQualifiedNamedTransform._resolve('apache_beam.Row')
 
   @patch('importlib.import_module')
-  def test_resolve(self, mock_import_module):
+  def test_resolve_by_path_segment(self, mock_import_module):
     mock_import_module.return_value = None
     with FullyQualifiedNamedTransform.with_filter('*'):
       FullyQualifiedNamedTransform._resolve('a.b.c.d')
     mock_import_module.assert_has_calls(
         [call('a'), call('a.b'), call('a.b.c'), call('a.b.c.d')])
 
+  def test_resolve(self):
+    # test _resolve with the module that is not exposed to the top level
+    with FullyQualifiedNamedTransform.with_filter('*'):
+      dataframe_transform = FullyQualifiedNamedTransform._resolve(
+          'apache_beam.dataframe.transforms.DataframeTransform')
+      from apache_beam.dataframe.transforms import DataframeTransform
+      self.assertIs(dataframe_transform, DataframeTransform)
+
+    # test _resolve with the module that will never be exposed
+    # to the top level in the future
+    with FullyQualifiedNamedTransform.with_filter('*'):
+      argument_placeholder = FullyQualifiedNamedTransform._resolve(
+          'apache_beam.internal.util.ArgumentPlaceholder')
+      from apache_beam.internal.util import ArgumentPlaceholder
+      self.assertIs(argument_placeholder, ArgumentPlaceholder)
+
 
 class _TestTransform(beam.PTransform):
   @classmethod