您必须使用side_effect
修补open
对象(mock_open
)的属性,并且不要忘记设置return_value
for__exit__
方法。
@patch('__builtin__.open', spec=open)
def test_interface_mapping(self, mock_open):
handle1 = MagicMock()
handle1.__enter__.return_value.__iter__.return_value = ('aa', 'bb')
handle1.__exit__.return_value=False
handle2 = MagicMock()
handle2.__enter__.return_value.__iter__.return_value = ('AA', 'BB')
handle2.__exit__.return_value=False
mock_open.side_effect = (handle1, handle2)
with open("ppp") as f:
self.assertListEqual(["aa","bb"],[x for x in f])
with open("ppp") as f:
self.assertListEqual(["AA","BB"],[x for x in f])
当在contextlib中使用时, 我发现一种更为优雅的方法来[模拟内置的“打开”功能
所以你可以重写测试像
@patch('__builtin__.open', new_callable=mock_open, read_data="aa\nbb")
def test_interface_mapping_new(self, mo):
handlers = (mo.return_value,mock_open(read_data="AA\nBB").return_value,)
mo.side_effect = handlers
with open("ppp") as f:
self.assertEqual("aa\nbb",f.read())
with open("ppp") as f:
self.assertEqual("AA\nBB",f.read())
从python 3.4开始,您还可以使用readline(),readlines()而不模拟其他任何东西。