def test_done():
counter = [0]
def inc(_):
counter[0] += 1
def dec(_):
counter[0] -= 1
p = Promise()
p.done(inc, dec)
p.fulfill(4)
assert_equals(counter[0], 1)
p = Promise()
p.done(inc, dec)
p.done(inc, dec)
p.reject(Exception())
assert_equals(counter[0], -1)
