def test_effective_amount (self):
charge = Charge(None, 10)
assert_equal(charge.effective_amount(), 10)
refund_1 = Mock(['amount'])
refund_1.amount = 1
charge.refunds.append(refund_1)
assert_equal(charge.effective_amount(), 9)
refund_2 = Mock(['amount'])
refund_2.amount = 2
charge.refunds.append(refund_2)
assert_equal(charge.effective_amount(), 7)
