pytest是否具有assertItemsEquity/assertCountEquity等效项

问题描述

unittest.TestCase有一个assertCountEqual method(Python2中的assertItemsEqual，可以说这是一个更好的名称)，它比较两个迭代并检查它们是否包含相同数量的相同对象，而不考虑它们的顺序。

pytest是否提供类似的功能？所有明显的替代方法(例如，文档中提到的在两端调用set(x)、sorted(x)或Counter(list(x)))都不起作用，因为我比较的是字典列表，而字典是不可哈希的。

---

解决方案

pytest不提供assertCountEqual，但我们可以只使用unittest的：

import unittest

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

而且输出也不错

$ 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:
First 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 ==========================

附注：the implementation of assertCountEqual包含专门针对不可散列类型的分支，does a bunch of bookkeeping and compares each item with every other item。