Question

lib.py

from django.core.urlresolvers import reverse
def render_reverse(f, kwargs):
    """
    kwargs is a dictionary, usually of the form {'args': [cbid]}
    """
    return reverse(f, **kwargs)

tests.py

from lib import render_reverse, print_ls

class LibTest(unittest.TestCase):

def test_render_reverse_is_correct(self):
    #with patch('webclient.apps.codebundles.lib.reverse') as mock_reverse:
    with patch('django.core.urlresolvers.reverse') as mock_reverse:
        from lib import render_reverse
        mock_f = MagicMock(name='f', return_value='dummy_views')
        mock_kwargs = MagicMock(name='kwargs',return_value={'args':['123']})
        mock_reverse.return_value = '/natrium/cb/details/123'
        response = render_reverse(mock_f(), mock_kwargs())

        print mock_reverse.mock_calls  # prints []
    print mock_reverse.mock_calls  # prints []
    self.assertTrue('/natrium/cb/details/' in response)

But instead, I get

  File "/var/lib/graphyte-webclient/graphyte-webenv/lib/python2.6/site-packages/django/core/urlresolvers.py", line 296, in reverse
    "arguments '%s' not found." % (lookup_view_s, args, kwargs))
NoReverseMatch: Reverse for 'dummy_readfile' with arguments '('123',)' and keyword arguments '{}' not found.

Why is it calling reverse instead of my mock_reverse (it is looking up my urls.py!!)
You can see calls returns an empty list. I even assert mock_reverse.called and it returned false.

Maybe I haven’t mentioned this, but lib is just a bunch of functions, there is no class.

Answer 1

Two things. 1. You need to patch reverse from Django. 2. You need to do import inside the context manager, to make lib module import mocked reverse.

from lib import print_ls

class LibTest(unittest.TestCase):

    def test_render_reverse_is_correct(self):
        with patch('django.core.urlresolvers.reverse') as mock_reverse:
            from lib import render_reverse
            mock_f = MagicMock(name='f', return_value='dummy_view')
            mock_kwargs = MagicMock(name='kwargs',return_value={'args':['123']})
            mock_reverse.return_value = '/natrium/cb/details/123'
            response = render_reverse(mock_f, mock_kwargs)

        self.assertTrue('/natrium/cb/details/' in response)