Django testing - fail on sending email - django

Question

I have a simple function in Django 1.4 that results in a mail being sent. This is put in a try/except, just in case the mailing service might be down (which is an external dependency).
Now, I would like to test this exception. I thought this would be simple, by overriding some email settings (like settings.EMAIL_HOST or settings.EMAIL_BACKEND) but Django test framework does not cause send_mail() to throw an error even if the backend is configured with jibberish...
So the question is: How do I make send_mail() throw an error in my test case?
Thanks!
Answer:
import mock
class MyTestCase(TestCase):
#mock.patch('path.to.your.project.views.send_mail', mock.Mock(side_effect=Exception('Boom!')))
def test_changed_send_mail(self):

Answer 1

I'm not a testing expert, but I think you should use a send_mail mock that raise the exception you want to test.
Probably you could take a look at this stackoverflow question to know more about mocking in Django.

Answer 2

Yes, the test suite does not set up the email system. Unfortunately, I don't know of any way t o test the email system.
You shouldn't really be testing send_mail functions as it is a built in. That said, you can validate the data being passed into send_mail by another function. If you know the domain of expected inputs, you can verify and throw (raise) an exception of your own.

Answer 3

https://docs.djangoproject.com/en/1.4/topics/email/#the-emailmessage-class
This is the more django'y way to send email:
# attempt to send out a welcome email
try :
t = loader.get_template('email_templates/membership/register.html')
c = Context({
'user' : user,
'site' : Site.objects.get(id=settings.SITE_ID)
})
msg = EmailMessage('Welcome to Site', t.render(c), settings.EMAIL_HOST_USER, to=[user.email,])
msg.content_subtype = "html"
msg.send()
except :
messages.info(request, _(u'Our email servers are encountering technical issues, you may not recieve a welcome email.'))
in my settings.py:
import os
EMAIL_HOST_USER = os.environ['SENDGRID_USERNAME']
EMAIL_HOST= 'smtp.sendgrid.net'
EMAIL_PORT = 587
EMAIL_USE_TLS = True
EMAIL_HOST_PASSWORD = os.environ['SENDGRID_PASSWORD']
note: SENDGRID_USERNAME and SENDGRID_PASSWORD are added as env variables by a heroku addon, you may have the actual credentials embedded in your settings file which is fine.
so why isnt your email throwing exceptions? https://docs.djangoproject.com/en/1.4/topics/email/#django.core.mail.get_connection
The fail_silently argument controls how the backend should handle errors. If fail_silently is True, exceptions during the email sending process will be silently ignored.

Answer 4

The patch documentation at http://www.voidspace.org.uk/python/mock/patch.html#where-to-patch explains in detail how to go about this.
I noted that the answer indeed was in the question but to help others understand where the catch is, the link above will prove to be quite insightful.
If you want to patch an object reference in class b.py, ensure that your patch call mocks the object reference in b.py rather than in a.py from where the object is imported. This can be a stumbling block for java developers who are getting used to the whole idea of functions being 1st class citizens.