Python 属性和单元测试 TestCase

Question

今天我写了测试，并在其中一种测试方法中打错了字。我的测试失败了，但我不明白为什么。是 Python 属性的特殊行为还是其他？

from unittest import TestCase


class FailObject(object):
    def __init__(self):
        super(FailObject, self).__init__()
        self.__action = None

    @property
    def action(self):
        return self.__action

    @action.setter
    def action(self, value):
        self.__action = value


def do_some_work(fcells, fvalues, action, value):
    currentFailObject = FailObject()
    rects = [currentFailObject]
    return rects


class TestModiAction(TestCase):
    def testSetFailObjectAction(self):
        rect = FailObject  # IMPORTANT PART
        rect.action = "SOME_ACTION" # No fail!
        self.assertEquals("SOME_ACTION", rect.action)

    def testSimple(self):
        fcells = []
        fvalues = []
        rects = do_some_work(fcells, fvalues, 'act', 0.56)

        rect = rects[0]
        self.assertEquals('act', rect.action)

当我用 Nose 测试运行这个测试用例时:

.F
======================================================================
FAIL: testSimple (test.ufsim.office.core.ui.cubeeditor.TestProperty.TestModiAction)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "TestProperty.py", line 36, in testSimple
    self.assertEquals('act', rect.action)
AssertionError: 'act' != 'SOME_ACTION'

----------------------------------------------------------------------
Ran 2 tests in 0.022s

FAILED (failures=1)

如果我通过在 testSetFailObjectAction 中创建实例来修复拼写错误，所有测试都会按预期进行。但是这个例子让我重新思考:使用属性安全吗？如果有一天我再次打字怎么办？

Answer 1

您可以使用 patch和 PropertyMock来自 mock对于这种工作:

@patch(__name__."FailObject.action", new_callable=PropertyMock, return_value="SOME_ACTION")
def testSetFailObjectAction(self, mock_action):
    self.assertEquals("SOME_ACTION", FailObject().action)
    self.assertTrue(mock_action.called)
    #This fail
    self.assertEquals("SOME_ACTION", FailObject.action)

通过 patch，您可以为测试上下文替换 action 属性，您还可以检查该属性是否已被使用。