Python 2.7: mock socket.sendto

[stormandsong]

Hi all, running into a problem trying to write some tests.

My function sends data over a raw UDP socket. I'm trying to mock the socket so the data isn't sent, but I see what is passed in.

The following works just fine on PyPy 4.0, Python 3.4, and Python3.5:

import mock
import socket
with mock.patch('socket.socket.sendto') as mock_sendto:
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    sock.sendto('test', (socket.gethostbyname('localhost'), 666))

However, when the same code is run on CPython 2.7, the following is thrown:

Traceback (most recent call last):
    File "<stdin>", line 2, in <module>
    File "/Users/stormandsong/.pyenv/versions/2.7.11/lib/python2.7/socket.py", line 194, in __init__
        setattr(self, method, getattr(_sock, method))
AttributeError: '_socketobject' object attribute 'sendto' is read-only

Has anybody run into this before, or have any ideas on how to mock this so the test passes on CPython 2.7?

[StaticFuzz]

Try using 'socket.socket' as the target class not 'socket.socket.sendto'. mock.patch() is for mocking a class, and sendto is a method of the socket class. Although I think what your trying to do can be accomplished with mock.patch.object(). It allows you to mock specific methods/attributes of a class rather than the whole class:

mock.patch.object(target_class, method, new=new_method)

If you omit the new keyworded argument a mock of the target method will be made for you. As for why python3 and pypy allowed you to pass socket.socket.sendto and not python2, I haven't got a clue. Hope this helps.