text: import unittest
  
  from torque.view.view_helper import mask_token
  
  
  class TestViewHelper(unittest.TestCase):
      def test_token_masked_4_last_chars_displayed(self):
          # arrange
          token = "66977d3f306941b1bbac8f58219f3f6f"
  
          # act
          masked_token = mask_token(token)
  
          # assert
          self.assertEqual(masked_token, "*********3f6f")
  
      def test_mask_token_returns_empty_string_when_called_without_token(self):
          self.assertEqual(mask_token(""), "")
          self.assertEqual(mask_token(None), "")
  