Home » Django » How can I unit test django messages?

How can I unit test django messages?

Posted by: admin November 30, 2017 Leave a comment

Questions:

In my django application, I’m trying to write a unit test that performs an action and then checks the messages in the response.

As far as I can tell, there is no nice way of doing this.

I’m using the CookieStorage storage method, and I’d like to do something similar to the following:

    response = self.client.post('/do-something/', follow=True)
    self.assertEquals(response.context['messages'][0], "fail.")

The problem is, all I get back is a

print response.context['messages']
<django.contrib.messages.storage.cookie.CookieStorage object at 0x3c55250>

How can I turn this into something useful, or am I doing it all wrong?

Thanks,
Daniel

Answers:

I did an experiment to test this. I changed the MESSAGE_STORAGE setting in one of my projects to 'django.contrib.messages.storage.cookie.CookieStorage' and executed a test that I had written to check for messages. It worked.

The key difference from what you were doing is the way I retrieved messages. See below:

def test_message_sending(self):
    data = dict(...)
    response = self.client.post(reverse('my_view'), data)
    messages = self.user.get_and_delete_messages()

    self.assertTrue(messages)
    self.assertEqual('Hey there!', messages[0])

This may be worth a try.

Questions:
Answers:

I found a really easy approach:

r = self.client.post('/foo/')
m = list(r.context['messages'])
self.assertEqual(len(m), 1)
self.assertEqual(str(m[0]), 'my message')

(I use session based backend for messages)

If you need to check for messages on a response that has no context you can use the following (thanks @benjaminGolder)

messages = list(r.wsgi_request._messages)
self.assertEqual(len(messages), 1)
self.assertEqual(str(messages[0]), 'my message')

The fallback storage doesn’t support indexing, however it is an iterable.

Questions:
Answers:

This works for me (displays all messages):

print [m.message for m in list(response.context['messages'])]

Also here are a couple of utility methods I have in a test class inherited from Django’s TestCase. If you’d prefer to have them as functions, remove the self arguments and replace self.fail()‘s with a raise.

def assert_message_count(self, response, expect_num):
    """
    Asserts that exactly the given number of messages have been sent.
    """

    actual_num = len(response.context['messages'])
    if actual_num != expect_num:
        self.fail('Message count was %d, expected %d' %
            (actual_num, expect_num))

def assert_message_contains(self, response, text, level=None):
    """
    Asserts that there is exactly one message containing the given text.
    """

    messages = response.context['messages']

    matches = [m for m in messages if text in m.message]

    if len(matches) == 1:
        msg = matches[0]
        if level is not None and msg.level != level:
            self.fail('There was one matching message but with different'
                'level: %s != %s' % (msg.level, level))

        return

    elif len(matches) == 0:
        messages_str = ", ".join('"%s"' % m for m in messages)
        self.fail('No message contained text "%s", messages were: %s' %
            (text, messages_str))
    else:
        self.fail('Multiple messages contained text "%s": %s' %
            (text, ", ".join(('"%s"' % m) for m in matches)))

def assert_message_not_contains(self, response, text):
    """ Assert that no message contains the given text. """

    messages = response.context['messages']

    matches = [m for m in messages if text in m.message]

    if len(matches) > 0:
        self.fail('Message(s) contained text "%s": %s' %
            (text, ", ".join(('"%s"' % m) for m in matches)))

Questions:
Answers:

From django documentation:

Outside of templates, you can use get_messages()

So, you could write something like:

from django.contrib.messages import get_messages

[...]

messages = [m.message for m in get_messages(response.wsgi_request)]
self.assertIn('My message', messages)

Questions:
Answers:

Simpler version of the stalemate one:

class TestCaseMessagesMixture(object):
    def assertMessageCount(self, response, expect_num):
        """
        Asserts that exactly the given number of messages have been sent.
        """

        actual_num = len(response.context['messages'])
        if actual_num != expect_num:
            self.fail('Message count was %d, expected %d' %
                    (actual_num, expect_num)
                )

    def assertMessageEqual(self, response, text):
        """
        Asserts that the response includes the message text.
        """

        messages = [m.message for m in response.context['messages']]

        if text not in messages:
            self.fail(
                'No message with text "%s", messages were: %s' % 
                    (text, messages)
                )

    def assertMessageNotEqual(self, response, text):
        """
        Asserts that the response does not include the message text.
        """

        messages = [m.message for m in response.context['messages']]

        if text in messages:
            self.fail(
                'Message with text "%s" found, messages were: %s' % 
                    (text, messages)
                )