Python properties and unittest TestCase

Today I wrote test and typoed in one of test methods. My tests failed but I don't understand why. Is it special behaviour of Python properties or something else?

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)

When I run this testcase with nose tests:

.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)

If I fix typo with instance creation in testSetFailObjectAction all tests are work as expected. But this example turn me back to question: Is it safe to use properties? What if I will typo again some day?