[TIP] Mocked subprocess.check_output fails assertion

[Chad Slater]

> It's sdterr vs. stderr, is there a typo in your assert_called_with?
>
> Regards,
> Thomas

That was it.  I stared at that problem for two hours and just didn't
see it. Thanks for catching that.

Regards,
Chad

On Sun, Feb 2, 2014 at 2:30 PM, Thomas Fenzl <thomas.fenzl at gmail.com> wrote:
> On 2014-02-02 22:05, Chad Slater wrote:
>> I'm having a rather strange problem, and I don't know if I'm doing
>> something boneheaded, or there's a bug in or limitation with mock.
>>
>> I'm able to successfully mock a call to subprocess.check_output.  When
>> I attempted to validate that it is called with the correct parameters,
>> the assert_called_with call fails; however, the printed output of the
>> failure appears to show that the correct values were called.
>>
>> An excerpt from the failure:
>> Expected call: check_output(['pw', 'group', 'add', '-n', 'testgroup',
>> '-g', '1010', '-M', 'bar'], sdterr=<MagicMock name='subprocess.STDOUT'
>> id='34418164624'>)
>> Actual call:   check_output(['pw', 'group', 'add', '-n', 'testgroup',
>> '-g', '1010', '-M', 'bar'], stderr=<MagicMock name='subprocess.STDOUT'
>> id='34418164624'>)
> It's sdterr vs. stderr, is there a typo in your assert_called_with?
>
> Regards,
> Thomas
>
>>
>> I'm assuming I'm patching this incorrectly, but looking through the
>> documentation for mock, I'm not sure I see where I went wrong. Full
>> details, including the function, and test case, are included below,
>> including imports, but file paths, group, and modules names have been
>> changed to protect the guilty.
>>
>>
>> ========================== Function in Module foo.py
>> ==================================
>> import subprocess
>>
>> from baz.exceptions import *
>>
>>
>> def create_group(name, gid):
>>     """Create a group called `name` with the `gid`.  Runs the following command
>>     on the host:
>>
>>     pw group add -n `name` -g `gid` -M bar
>>
>>     :param name: the group name
>>     :type name: `str`
>>     :param gid: the group id
>>     :type gid: `int`
>>
>>     .. Warning:: Use :func:`get_gid` to find a valid gid and avoid potential
>>     security implications or other errors.
>>
>>     """
>>     cmd = ["pw", "group", "add", "-n", name, "-g", str(gid), "-M", "bar"]
>>     try:
>>         out = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
>>
>>    except subprocess.CalledProcessError as cpe:
>>         print cpe.output
>>         return False
>>
>>     except OSError as ose:
>>         print ose
>>         return False
>>     return True
>>
>> ========================== Test Module =========================================
>> import re
>> from unittest import TestCase
>> try:                                                # If we're running
>> Python3, mock is built-in to unnittest
>>     from unittest.mock import patch, mock_open, MagicMock, ANY
>> except ImportError:
>>     from mock import patch, mock_open, Mock, MagicMock, ANY
>>
>> from baz.buzz import foo
>> from bazz.exceptions import *
>> from bazz.buzz.test.test_data import TEST_DATA1, TEST_DATA2, TEST_DATA3
>>
>> class TestCreateGroup(TestCase):
>>
>>     @patch('foo.subprocess')
>>     def test_create_group_cmds(self, mock_sp):
>>         name = "testgroup"
>>         gid = 1010
>>         res = executor.create_group(name, gid)
>>         cmd = ["pw", "group", "add", "-n", name, "-g", str(gid), "-M", "bar"]
>>         mock_sp.check_output.assert_called_with(cmd, sdterr=mock_sp.STDOUT)
>>
>> ========================= Test Results =========================================
>>
>> Failure
>> Traceback (most recent call last):
>>   File "/path/to/venv/lib/python2.7/site-packages/mock.py", line 1201,
>> in patched
>>     return func(*args, **keywargs)
>>   File "/path/to/app/test/executor_tests.py", line 234, in
>> test_create_group_cmds
>>     mock_sp.check_output.assert_called_with(cmd, sdterr=mock_sp.STDOUT)
>>   File "/path/to/venv/lib/python2.7/site-packages/mock.py", line 835,
>> in assert_called_with
>>     raise AssertionError(msg)
>> AssertionError: Expected call: check_output(['pw', 'group', 'add',
>> '-n', 'testgroup', '-g', '1010', '-M', 'bar'], sdterr=<MagicMock
>> name='subprocess.STDOUT' id='34418164624'>)
>> Actual call: check_output(['pw', 'group', 'add', '-n', 'testgroup',
>> '-g', '1010', '-M', 'bar'], stderr=<MagicMock name='subprocess.STDOUT'
>> id='34418164624'>)
>>
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>