How do I patch django.core.mail.send_mail for testing?

[Andrew Farrell]

Hi folks,

I'm trying to use mock.patch to test that a particular post-save signal kicks off an email. My current approach to this is...

from django.test import TestCase

from mock import patch

class RegisterTestCase(TestCase):

    def test_mail_is_sent(self):

        with patch('django.core.mail.send_mail') as mocked_send_mail:

            from register.models import Subscriber  #This test still fails if I have the import outside the mock context

            subscriber = Subscriber.objects.create(

                email = 'te...@example.com',

            )

            self.assertTrue(mocked_send_mail.called)

            self.assertFalse(subscriber.active)

            self.assertEqual(mocked_send_mail.call_args['recipient_list'], 'te...@example.com')

    def test_patching_mail_works(self):

        with patch('django.core.mail.send_mail') as mocked_send_mail:

            from django.core.mail import send_mail   #This test actually fails too if I have the import outside the mock context

            send_mail(subject="foo", message="bar", from_email="Andrew M. Farrell <amfa...@mit.edu>",

                recipient_list = ['Andrew M. Farrell <amfa...@mit.edu>',])

            self.assertTrue(mocked_send_mail.called)

The first test fails while the second test passes.

As I understand from reading the mock.patch documentation, patch('django.core.mail.send_mail') should cause all references to that object to instead referr to an instance of MagicMock.

However, I can verify by inserting a pdb.set_trace() call into the signal handler that send_mail is in fact called during the test and that send_mail.func_code is <code object send_mail at 0x103492330, file "//anaconda/envs/taxbrain/lib/python2.7/site-packages/django/core/mail/__init__.py", line 41>. 

Are there other things that could cause a function to not be mocked properly?

Is my interpretation of the documentation just incorrect?

thank you,

Andrew

[Stephen J. Butler]

I think you instead want to use self.modify_settings() or
self.override_settings() to change EMAIL_BACKEND to locmem:

https://docs.djangoproject.com/en/1.8/topics/email/#in-memory-backend

Then you can inspect django.core.mail.outbox to verify recipients, message, etc.

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[sclo...@nexapp.ca]

I solved the problem by wrapping the imports of the test-file inside a context manager, as follow:

with patch('django.core.mail.send_mail') as mocked_send_mail:

    from ModuleToTest.File import functionToTest

That forced the patch to occur before the tested function was actualy imported.