我可以在 python 单元测试中伪造/模拟我的模拟对象的类型吗

2022-01-08 00:00:00 python mocking unit-testing

问题描述

在我的 python 代码中，我检查其中一个参数的类型以确保它是我期望的类型.例如:

In my python code I check the type of one of the parameters to make sure it is of the type I expect. For instance: 

def myfunction(dbConnection):
    if (type(dbConnection)<>bpgsql.Connection):
        r['error'] += ' invalid database connection'

我想传递一个模拟连接以进行测试.有没有办法让模拟对象伪装成正确的类型?

I want to pass a mock connection for testing purposes. Is there a way to make the mock object pretend to be of the correct type?

解决方案

恕我直言，看来你们不太对劲！

With all due respect, It looks like you guys are not quite right!

如上所述，我可以使用鸭子打字，但有一种方法可以做我最初打算做的事情:

I can use duck typing as said, but there is a way to do what I intended to do in the first place:

来自 http://docs.python.org/dev/library/unittest.mock.html

使用类或实例作为 spec 或 spec_set 的模拟对象能够通过 isintance 测试:

Mock objects that use a class or an instance as a spec or spec_set are able to pass isintance tests: 

>>>
>>> mock = Mock(spec=SomeClass)
>>> isinstance(mock, SomeClass)
True
>>> mock = Mock(spec_set=SomeClass())
>>> isinstance(mock, SomeClass)
True

所以我的示例代码如下:

so my example code would be like: 

m = mock.MagicMock(spec=bpgsql.Connection)
isinstance(m, bpgsql.Connection)

返回真

话虽如此，我并不是在争论在 python 中进行严格的类型检查，我说如果你需要检查它你可以做到，它也适用于测试和模拟.

All that said, I am not arguing for strict type checking in python, I say if you need to check it you can do it and it works with testing and mocking too.

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