def test_assign_average_using_B(self):
     self.assertEqual(a.switch_average('B'), 80)
 def test_assign_average_using_A(self):
     self.assertEqual(a.switch_average('A'), 90)
 def test_assign_average_using_invalid_key(self):
     self.assertEqual(a.switch_average('Z'), 'Value not found for Z.')
 def test_assign_average_using_F(self):
     self.assertEqual(a.switch_average('F'), 0)
 def test_assign_average_using_D(self):
     self.assertEqual(a.switch_average('D'), 60)
 def test_assign_average_using_C(self):
     self.assertEqual(a.switch_average('C'), 70)