new_contents: import unittest
  import color_contrast_calc
  
  class TestColorContrastCalc(unittest.TestCase):
      def setUp(self):
          pass
  
      def test_color(self):
          yellow = color_contrast_calc.color.Color.from_name('yellow')
          black = color_contrast_calc.color.Color.from_name('black')
  
          contrast_ratio = yellow.contrast_ratio_against(black)
          self.assertAlmostEqual(contrast_ratio, 19.56, 2)
  
subject: add tests for color_contrast_calc