old_contents: import os
  
  from tests.basic_env import TestDvc
  
  
  class TestIsDvcInternal(TestDvc):
      def test_return_false_on_non_dvc_file(self):
          path = os.path.join("path", "to-non-.dvc", "file")
          self.assertFalse(self.dvc.is_dvc_internal(path))
  
      def test_return_true_on_dvc_internal_file(self):
          path = os.path.join("path", "to", ".dvc", "file")
          self.assertTrue(path)
  
new_contents: from dvc.utils.compat import fspath
  
  
  def test_is_dvc_internal(tmp_dir, dvc):
      assert dvc.is_dvc_internal(fspath(tmp_dir / ".dvc" / "file"))
      assert not dvc.is_dvc_internal("file")
  
subject: use pytest