问题描述
类 HelloWorld(object):def say_it(self):返回'你好我是你好世界'def i_call_hello_world(hw_obj):print 'here... 检查类型:%s' %type(HelloWorld)如果是实例(hw_obj,HelloWorld):打印 hw_obj.say_it()来自模拟导入补丁,MagicMock导入单元测试类TestInstance(unittest.TestCase):@patch('__main__.HelloWorld', spec=HelloWorld)def test_mock(self,MK):印刷类型(MK)MK.say_it.return_value = '我是假的'v = i_call_hello_world(MK)打印 v如果 __name__ == '__main__':c = 你好世界()i_call_hello_world(c)打印 isinstance(c, HelloWorld)单元测试.main()
这是回溯
这里...检查类型:<type 'type'>你好我是你好世界真的<类'mock.MagicMock'>这里...检查类型:<class 'mock.MagicMock'>乙=========================================================================错误:test_mock (__main__.TestInstance)----------------------------------------------------------------------回溯(最近一次通话最后):文件/usr/local/lib/python2.7/dist-packages/mock.py",第 1224 行,已修补返回函数(*args,**keywargs)文件t.py",第 18 行,在 test_mockv = i_call_hello_world(MK)i_call_hello_world 中的文件t.py",第 7 行如果是实例(hw_obj,HelloWorld):TypeError: isinstance() arg 2 必须是类、类型或类和类型的元组----------------------------------------------------------------------在 0.002 秒内运行 1 次测试
Q1.为什么会抛出这个错误?它们是 <class type='MagicMock>
Q2.如果错误得到修复,如何暂停模拟以便第一行通过?
来自 文档:p><块引用>
通常,对象的 __class__ 属性将返回其类型.对于具有规范的模拟对象,__class__ 改为返回规范类.这允许模拟对象通过 isinstance() 测试它们正在替换/伪装为的对象:
mock = Mock(spec=3)isinstance(模拟,int)真的
不要使用 isinstance,而是检查 say_it 方法是否存在.如果方法存在,调用它:
if hasattr(hw_obj, 'say_it'):打印 hw_obj.say_it()
无论如何,这是一个更好的设计:依赖类型信息更加脆弱.
class HelloWorld(object): def say_it(self): return 'Hello I am Hello World' def i_call_hello_world(hw_obj): print 'here... check type: %s' %type(HelloWorld) if isinstance(hw_obj, HelloWorld): print hw_obj.say_it() from mock import patch, MagicMock import unittest class TestInstance(unittest.TestCase): @patch('__main__.HelloWorld', spec=HelloWorld) def test_mock(self,MK): print type(MK) MK.say_it.return_value = 'I am fake' v = i_call_hello_world(MK) print v if __name__ == '__main__': c = HelloWorld() i_call_hello_world(c) print isinstance(c, HelloWorld) unittest.main()
Here is the traceback
here... check type: <type 'type'> Hello I am Hello World True <class 'mock.MagicMock'> here... check type: <class 'mock.MagicMock'> E ====================================================================== ERROR: test_mock (__main__.TestInstance) ---------------------------------------------------------------------- Traceback (most recent call last): File "/usr/local/lib/python2.7/dist-packages/mock.py", line 1224, in patched return func(*args, **keywargs) File "t.py", line 18, in test_mock v = i_call_hello_world(MK) File "t.py", line 7, in i_call_hello_world if isinstance(hw_obj, HelloWorld): TypeError: isinstance() arg 2 must be a class, type, or tuple of classes and types ---------------------------------------------------------------------- Ran 1 test in 0.002s
Q1. Why is this error thrown? They are <class type='MagicMock>
Q2. How do I pause the mocking so that the first line will pass if the error is fixed?
From the docs:
Normally the __class__ attribute of an object will return its type. For a mock object with a spec, __class__ returns the spec class instead. This allows mock objects to pass isinstance() tests for the object they are replacing / masquerading as:
mock = Mock(spec=3) isinstance(mock, int) True
Don't use isinstance, instead check for the existence of the say_it method. If the method exists, call it:
if hasattr(hw_obj, 'say_it'): print hw_obj.say_it()
This is a better design anyway: relying on type information is much more brittle.
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