(self):
self.assertEqual(self.test_printing.get_printing_cost(), 0)

def test_get_total_cost(self):
self.assertEqual(self.test_printing.get_total_cost(), 0)

def test_add_printing(self):
self.test_printing.add_printing('A4', 5, 0.5)
self.assertEqual(self.test_printing.get_total_cost(), 2.5)

def test__str__(self):
self.assertEqual(str(self.test