import unittest
from billing import total

class TotalTests(unittest.TestCase):
    def test_empty(self):
        self.assertEqual(total([]), 0)
    def test_one_item(self):
        self.assertEqual(total([12]), 12)
    def test_multiple_items(self):
        self.assertEqual(total([10, 20, 30]), 60)
    def test_zero(self):
        self.assertEqual(total([0, 5]), 5)

if __name__ == "__main__":
    unittest.main()