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from tests import TestCase
from exam import Exam, fixture
from exam.asserts import AssertsMixin
class AssertChangesMixin(Exam, TestCase):
case = fixture(AssertsMixin)
thing = fixture(list)
def no_op_context(self, *args, **kwargs):
with self.case.assertChanges(len, self.thing, *args, **kwargs):
pass
def test_checks_change_on_callable_passed(self):
with self.case.assertChanges(len, self.thing, before=0, after=1):
self.thing.append(1)
def test_after_check_asserts_ends_on_after_value(self):
self.thing.append(1)
with self.case.assertChanges(len, self.thing, after=2):
self.thing.append(1)
def test_before_check_asserts_starts_on_before_value(self):
self.thing.append(1)
with self.case.assertChanges(len, self.thing, before=1):
self.thing.append(1)
self.thing.append(2)
def test_verifies_value_must_change_no_matter_what(self):
self.thing.append(1)
with self.assertRaises(AssertionError):
self.no_op_context(after=1)
with self.assertRaises(AssertionError):
self.no_op_context(before=1)
with self.assertRaises(AssertionError):
self.no_op_context()
def test_reraises_exception_if_raised_in_context(self):
with self.assertRaises(NameError):
with self.case.assertChanges(len, self.thing, after=5):
self.thing.append(1)
undefined_name
def test_does_not_change_passes_if_no_change_was_made(self):
with self.assertDoesNotChange(len, self.thing):
pass
def test_raises_assertion_error_if_value_changes(self):
msg = 'Value changed from 0 to 1'
with self.assertRaisesRegexp(AssertionError, msg):
with self.assertDoesNotChange(len, self.thing):
self.thing.append(1)
def test_assertion_error_mentions_unexpected_result_at_after(self):
msg = 'Value changed to 1, not 3'
with self.assertRaisesRegexp(AssertionError, msg):
with self.assertChanges(len, self.thing, after=3):
self.thing.append(1)
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