Django file and memory mail back-end for tests

Whenever you write unit or integration tests for your Django application that involves sending mails, you end up with the LocMem mail back-end (django.core.mail.backends.console .EmailBackend) as a default set by Django during test setup. However, if you want to have a look at all the mails that have been sent, you are probably going to choose the File mail back-end (django.core.mail.backends.filebased.EmailBackend) [docs].

The former give you the possibility to check for the amount of mails that have been sent and inspect them further through django.core.mail.outbox, the latter stores all mails in a text file for later inspection.

So, if you are using the LocMem back-end and want to inspect all mails after an entire test run, you are first trying to change the back-end with @override_settings [docs]. This works as long as you don’t use django.core.mail.outbox, because this will always be None or []. How are you going to make that work?

When this question came up on the Django IRC channel I’ll came up with

import django
from django.core import mail
from django.core.mail.backends.filebased import EmailBackend as FileEmailBackend


class EmailBackend(FileEmailBackend):
    def __init__(self, *args, **kwargs):
        super(EmailBackend, self).__init__(*args, **kwargs)
        if not hasattr(mail, 'outbox'):
            mail.outbox = []

    def write_message(self, message):
        if django.VERSION[:2] > (1, 5):
            super(EmailBackend, self).write_message(message)
            mail.outbox.append(message)

    def send_messages(self, messages):
        ret = super(EmailBackend, self).send_messages(messages)
        if django.VERSION[:2] < (1, 6):
            mail.outbox.extend(messages)
        return ret

I didn’t test the code myself, but the user asking for support seemed to find it a working solution.