new_contents: import unittest
  from itertools import chain
  
  from apriori import subsets
  
  
  class AprioriTest(unittest.TestCase):
      def test_subsets_should_return_empty_subsets_if_input_empty_set(self):
          result = tuple(subsets(set([])))
  
          self.assertEqual(result, ())
  
      def test_subsets_should_return_non_empty_subsets(self):
          result = tuple(subsets(set(['beer', 'rice'])))
  
          self.assertEqual(result[0], ('beer',))
          self.assertEqual(result[1], ('rice',))
          self.assertEqual(result[2], ('beer', 'rice',))
  
  
  if __name__ == '__main__':
      unittest.main()
  
subject: Test subsets method