Does pytest have an assertItemsEqual / assertCountEqual equivalent

Question

unittest.TestCase has an assertCountEqual method (assertItemsEqual in Python 2, which is arguably a better name), which compares two iterables and checks that they contain the same number of the same objects, without regard for their order.

Does pytest provide something similar? All of the obvious alternatives (e.g. calling set(x), sorted(x) or Counter(list(x)) on each side as mentioned in the documentation) don't work, because the things I'm comparing are lists of dictionaries, and dictionaries aren't hashable.

Answer 1

pytest does not provide an assertCountEqual, but we can just use unittest's:

import unittest  def test_stuff():     case = unittest.TestCase()     a = [{'a': 1}, {'b': 2}]     b = [{'b': 2}]     case.assertCountEqual(a, b) 

And the output is decent, too

$ py.test ============================= test session starts ============================== platform linux -- Python 3.6.2, pytest-3.2.1, py-1.4.34, pluggy-0.4.0 rootdir: /home/they4kman/.virtualenvs/tmp-6626234b42fb350/src, inifile: collected 1 item  test_stuff.py F  =================================== FAILURES =================================== __________________________________ test_stuff __________________________________      def test_stuff():         case = unittest.TestCase()         a = [{'a': 1}, {'b': 2}]         b = [{'b': 2}] >       case.assertCountEqual(a, b)  test_stuff.py:7: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ /usr/lib/python3.6/unittest/case.py:1182: in assertCountEqual     self.fail(msg) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  self = <unittest.case.TestCase testMethod=runTest> msg = "Element counts were not equal:\nFirst has 1, Second has 0:  {'a': 1}"      def fail(self, msg=None):         """Fail immediately, with the given message.""" >       raise self.failureException(msg) E       AssertionError: Element counts were not equal: E       First has 1, Second has 0:  {'a': 1}  /usr/lib/python3.6/unittest/case.py:670: AssertionError =========================== 1 failed in 0.07 seconds ========================== 

Side note: the implementation of assertCountEqual includes a branch specifically for unhashable types, which does a bunch of bookkeeping and compares each item with every other item.