def test_main(self):
func = deal.post(lambda x: x > 0)(lambda x: -x)
with self.subTest(text='good'):
self.assertEqual(func(-4), 4)
with self.subTest(text='error'):
with self.assertRaises(deal.PostContractError):
func(4)
def test_source_get_chain():
sum_contract = deal.chain(
deal.pre(lambda a, b: a > 0),
deal.pre(lambda a, b: b > 0),
deal.post(lambda res: res > 0),
)
@sum_contract
def sum(a, b):
return a + b
with pytest.raises(deal.ContractError) as exc_info:
sum(-2, 3)
assert exc_info.value.source == 'a > 0'
with pytest.raises(deal.ContractError) as exc_info:
sum(2, -3)
assert exc_info.value.source == 'b > 0'
state.color = False
assert str(exc_info.value) == 'expected b > 0 (where a=2, b=-3)'
state.color = True
def test_return_value_fulfils_contract(self):
func = deal.post(lambda x: x > 0)(lambda x: -x)
assert func(-4) == 4
with pytest.raises(deal.PostContractError):
func(4)
# built-in
from typing import List
# external
import pytest
# project
import deal
# if you have more than 2-3 contracts,
# consider moving them from decorators into separate variable
# like this:
contract_for_index_of = deal.chain(
# result is an index of items
deal.post(lambda result: result >= 0),
deal.ensure(lambda items, item, result: result < len(items)),
# element at this position matches item
deal.ensure(
lambda items, item, result: items[result] == item,
message='invalid match',
),
# element at this position is the first match
deal.ensure(
lambda items, item, result: not any(el == item
for el in items[:result]),
message='not the first match',
),
# LookupError will be raised if no elements found
deal.raises(LookupError),
deal.reason(LookupError, lambda items, item: item not in items),
# no side-effects
