Testing Consumers

When you want to write unit tests for your new Channels consumers, you’ll realize that you can’t use the standard Django test client to submit fake HTTP requests - instead, you’ll need to submit fake Messages to your consumers, and inspect what Messages they send themselves.

We provide a TestCase subclass that sets all of this up for you, however, so you can easily write tests and check what your consumers are sending.

ChannelTestCase

If your tests inherit from the channels.tests.ChannelTestCase base class, whenever you run tests your channel layer will be swapped out for a captive in-memory layer, meaning you don’t need an external server running to run tests.

Moreover, you can inject messages onto this layer and inspect ones sent to it to help test your consumers.

To inject a message onto the layer, simply call Channel.send() inside any test method on a ChannelTestCase subclass, like so:

from channels import Channel
from channels.tests import ChannelTestCase

class MyTests(ChannelTestCase):
    def test_a_thing(self):
        # This goes onto an in-memory channel, not the real backend.
        Channel("some-channel-name").send({"foo": "bar"})

To receive a message from the layer, you can use self.get_next_message(channel), which handles receiving the message and converting it into a Message object for you (if you want, you can call receive_many on the underlying channel layer, but you’ll get back a raw dict and channel name, which is not what consumers want).

You can use this both to get Messages to send to consumers as their primary argument, as well as to get Messages from channels that consumers are supposed to send on to verify that they did.

You can even pass require=True to get_next_message to make the test fail if there is no message on the channel (by default, it will return you None instead).

Here’s an extended example testing a consumer that’s supposed to take a value and post the square of it to the "result" channel:

from channels import Channel
from channels.tests import ChannelTestCase

class MyTests(ChannelTestCase):
    def test_a_thing(self):
        # Inject a message onto the channel to use in a consumer
        Channel("input").send({"value": 33})
        # Run the consumer with the new Message object
        my_consumer(self.get_next_message("input", require=True))
        # Verify there's a result and that it's accurate
        result = self.get_next_message("result", require=True)
        self.assertEqual(result['value'], 1089)

Generic Consumers

You can use ChannelTestCase to test generic consumers as well. Just pass the message object from get_next_message to the constructor of the class. To test replies to a specific channel, use the reply_channel property on the Message object. For example:

from channels import Channel
from channels.tests import ChannelTestCase

from myapp.consumers import MyConsumer

class MyTests(ChannelTestCase):

    def test_a_thing(self):
        # Inject a message onto the channel to use in a consumer
        Channel("input").send({"value": 33})
        # Run the consumer with the new Message object
        message = self.get_next_message("input", require=True)
        MyConsumer(message)
        # Verify there's a reply and that it's accurate
        result = self.get_next_message(message.reply_channel.name, require=True)
        self.assertEqual(result['value'], 1089)

Groups

You can test Groups in the same way as Channels inside a ChannelTestCase; the entire channel layer is flushed each time a test is run, so it’s safe to do group adds and sends during a test. For example:

from channels import Group
from channels.tests import ChannelTestCase

class MyTests(ChannelTestCase):
    def test_a_thing(self):
        # Add a test channel to a test group
        Group("test-group").add("test-channel")
        # Send to the group
        Group("test-group").send({"value": 42})
        # Verify the message got into the destination channel
        result = self.get_next_message("test-channel", require=True)
        self.assertEqual(result['value'], 42)

Clients

For more complicated test suites you can use the Client abstraction that provides an easy way to test the full life cycle of messages with a couple of methods: send to sending message with given content to the given channel, consume to run appointed consumer for the next message, receive to getting replies for client. Very often you may need to send and than call a consumer one by one, for this purpose use send_and_consume method:

from channels.tests import ChannelTestCase, Client

class MyTests(ChannelTestCase):

    def test_my_consumer(self):
        client = Client()
        client.send_and_consume('my_internal_channel', {'value': 'my_value'})
        self.assertEqual(client.receive(), {'all is': 'done'})

You can use HttpClient for websocket related consumers. It automatically serializes JSON content, manage cookies and headers, give easy access to the session and add ability to authorize your requests. For example:

# consumers.py
class RoomConsumer(JsonWebsocketConsumer):
    http_user = True
    groups = ['rooms_watchers']

    def receive(self, content, **kwargs):
        self.send({'rooms': self.message.http_session.get("rooms", [])})
        Channel("rooms_receive").send({'user': self.message.user.id,
                                       'message': content['message']}


# tests.py
from channels import Group
from channels.tests import ChannelTestCase, HttpClient


class RoomsTests(ChannelTestCase):

    def test_rooms(self):
        client = HttpClient()
        user = User.objects.create_user(username='test', email='test@test.com',
                                        password='123456') # fuck you security
        client.login(username='test', password='123456')

        client.send_and_consume('websocket.connect', '/rooms/')
        # check that there is nothing to receive
        self.assertIsNone(client.receive())

        # test that the client in the group
        Group(RoomConsumer.groups[0]).send({'text': 'ok'}, immediately=True)
        self.assertEqual(client.receive(json=False), 'ok')

        client.session['rooms'] = ['test', '1']
        client.session.save()

        client.send_and_consume('websocket.receive',
                                text={'message': 'hey'},
                                path='/rooms/')
        # test 'response'
        self.assertEqual(client.receive(), {'rooms': ['test', '1']})

        self.assertEqual(self.get_next_message('rooms_receive').content,
                         {'user': user.id, 'message': 'hey'})

        # There is nothing to receive
        self.assertIsNone(client.receive())

Instead of HttpClient.login method with credentials at arguments you may call HttpClient.force_login (like at django client) with the user object.

receive method by default trying to deserialize json text content of a message, so if you need to pass decoding use receive(json=False), like in the example.

Applying routes

When you need to testing you consumers without routes in settings or you want to testing your consumers in more isolate and atomic way, it will be simpler with apply_routes contextmanager and decorator for your ChannelTestCase. It takes list of routes that you want to use and overwrite existing routes:

from channels.tests import ChannelTestCase, HttpClient, apply_routes

class MyTests(ChannelTestCase):

    def test_myconsumer(self):
        client = HttpClient()

        with apply_routes([MyConsumer.as_route(path='/new')]):
            client.send_and_consume('websocket.connect', '/new')
            self.assertEqual(client.receive(), {'key': 'value'})

Test Data binding with HttpClient

As you know data binding in channels works in outbound and inbound ways, so that ways tests in different ways and HttpClient and apply_routes will help to do this. When you testing outbound consumers you need just import your Binding subclass with specified group_names. At test you can join to one of them, make some changes with target model and check received message. Lets test IntegerValueBinding from data binding with creating:

from channels.tests import ChannelTestCase, HttpClient
from channels.signals import consumer_finished

class TestIntegerValueBinding(ChannelTestCase):

    def test_outbound_create(self):
        # We use HttpClient because of json encoding messages
        client = HttpClient()
        client.join_group("intval-updates")  # join outbound binding

        # create target entity
        value = IntegerValue.objects.create(name='fifty', value=50)

        consumer_finished.send(sender=None)
        received = client.receive()  # receive outbound binding message
        self.assertIsNotNone(received)

        self.assertTrue('payload' in received)
        self.assertTrue('action' in received['payload'])
        self.assertTrue('data' in received['payload'])
        self.assertTrue('name' in received['payload']['data'])
        self.assertTrue('value' in received['payload']['data'])

        self.assertEqual(received['payload']['action'], 'create')
        self.assertEqual(received['payload']['model'], 'values.integervalue')
        self.assertEqual(received['payload']['pk'], value.pk)

        self.assertEqual(received['payload']['data']['name'], 'fifty')
        self.assertEqual(received['payload']['data']['value'], 50)

        # assert that is nothing to receive
        self.assertIsNone(client.receive())

There is another situation with inbound binding. It is used with WebSocket Multiplexing, So we apply two routes: websocket route for demultiplexer and route with internal consumer for binding itself, connect to websocket entrypoint and test different actions. For example:

class TestIntegerValueBinding(ChannelTestCase):

    def test_inbound_create(self):
        # check that initial state is empty
        self.assertEqual(IntegerValue.objects.all().count(), 0)

        with apply_routes([Demultiplexer.as_route(path='/'),
                          route("binding.intval", IntegerValueBinding.consumer)]):
            client = HttpClient()
            client.send_and_consume('websocket.connect', path='/')
            client.send_and_consume('websocket.receive', path='/', text={
                'stream': 'intval',
                'payload': {'action': CREATE, 'data': {'name': 'one', 'value': 1}}
            })
            # our Demultiplexer route message to the inbound consumer,
            # so we need to call this consumer
            client.consume('binding.users')

        self.assertEqual(IntegerValue.objects.all().count(), 1)
        value = IntegerValue.objects.all().first()
        self.assertEqual(value.name, 'one')
        self.assertEqual(value.value, 1)

Multiple Channel Layers

If you want to test code that uses multiple channel layers, specify the alias of the layers you want to mock as the test_channel_aliases attribute on the ChannelTestCase subclass; by default, only the default layer is mocked.

You can pass an alias argument to get_next_message, Client and Channel to use a different layer too.