class TestNode(unittest.TestCase):
    def setUp(self):
        self.node = Node()
        self.callback_call_count = 0

    def testEq(self):
        self.assertEqual(self.node, Node())

    def testNe(self):
        self.assertNotEqual(self.node, None)

    def testWalk(self):
        self.node.walk(self.callback)
        self.assertEqual(self.callback_call_count, 1)

    def callback(self, node):
        self.callback_call_count += 1
 def setUp(self):
     self.node = Node()
     self.callback_call_count = 0