new_contents: import unittest
  from textinator import calculate_size
  
  class CalculateSizeTestCase(unittest.TestCase):
      """Tests for calculate_size()"""
  
      def test_width_no_height(self):
          self.assertEqual(calculate_size((1920, 1080), (20, None)),
                      (20, 11))
          self.assertEqual(calculate_size((500, 1240), (200, None)),
                      (200, 496))
  
      def test_height_no_width(self):
          self.assertEqual(calculate_size((1024, 768), (None, 413)),
                      (551, 413))
          self.assertEqual(calculate_size((10, 670), (None, 800)),
                      (12, 800))
  
      def test_height_and_width(self):
          self.assertEqual(calculate_size((500, 600), (42, 612)),
                      (42, 612))
  
  if __name__ == '__main__':
      unittest.main()
  
subject: Add basic tests