Running django tests with selenium in docker

Question

For executing tests I usually run a separate container with:

docker-compose run --rm web /bin/bash

Where web is a container with django. From a shell I execute py.test from time to time.

In order to be able to reach selenium from a container with django and to allow the browser from selenium container to reach django's liveserver I decided to use "net" parameter which allows containers to share net. So I added it to the yml:

selenium:
    image: selenium/standalone-firefox
    net: "container:web"

Unfortunately this does not work. I do not see 4444 port in my django container.

It only works if instead of net:"container:web" I specify an autogenerated container's name, like net:"container:project_web_run_1" .

Also I tried instead of docker-compose run --rm .... use docker-compose up --no-deps changing command parameter to py.test functional_tests but that did not work either.

Is this the right of using selenium with containers?

Answer 1

Here is how I do it. The basic problem is that docker-compose run will generate a different hostname (project_container_run_x) where x is hard to know for sure. I ended up just going off of ip address. I'm also ensuring DEBUG is False otherwise I get a bad request.

I'm using StaticLiveServerTestCase like this:

import os
import socket

os.environ['DJANGO_LIVE_TEST_SERVER_ADDRESS'] = '0.0.0.0:8000'

class IntegrationTests(StaticLiveServerTestCase):
    live_server_url = 'http://{}:8000'.format(
        socket.gethostbyname(socket.gethostname())
    )

    def setUp(self):
        settings.DEBUG = True
        self.browser = webdriver.Remote(
            command_executor="http://selenium:4444/wd/hub",
            desired_capabilities=DesiredCapabilities.CHROME
        )

    def tearDown(self):
        self.browser.quit()
        super().tearDown()

    def test_home(self):
        self.browser.get(self.live_server_url)

My docker-compose file has this for selenium and extends the web container (where django is running). Port 5900 is open for VNC. I like to keep this isolated in something like docker-compose.selenium.yml

version: '2'
services:
  web:
    environment:
      SELENIUM_HOST: http://selenium:4444/wd/hub
      TEST_SELENIUM: 'yes'
    depends_on:
      - selenium

  selenium:
    image: selenium/standalone-chrome-debug
    ports:
      - "5900:5900"

I can run tests like

docker-compose run --rm web ./manage.py test

So my web container is accessing selenium via the "selenium" host. Selenium then accesses the web container by ip address which is determined on the fly.

Another gotcha is that it's tempting to just use "web" as the hostname. If your docker-compose run command starts up a separate web container - this will appear to work. However it won't be using your test database, making for not a great test.

Answer 2

For anyone running pytest, and possibly pytest-splinter (Selenium wrapper)

version: '3'
services:
  db:
    image: postgres
  django:
    build: .
    ports: 
      - "8000:8000"
    depends_on:
      - db
      - selenium
  selenium:
    image: selenium/standalone-firefox-debug:latest
    ports:
      - "4444:4444"   # Selenium
      - "5900:5900"   # VNC 

Define a conftest.py in your root directory to make these fixtures available to all your tests

import socket

import pytest
from pytest_django.live_server_helper import LiveServer


@pytest.fixture(scope='session')
def test_server() -> LiveServer:
    addr = socket.gethostbyname(socket.gethostname())
    server = LiveServer(addr)
    yield server
    server.stop()


@pytest.fixture(autouse=True, scope='function')
def _test_server_helper(request):
    """
    Configures test_server fixture so you don't have to mark
    tests with @pytest.mark.django_db
    """
    if "test_server" not in request.fixturenames:
        return

    request.getfixturevalue("transactional_db")


# Settings below here are exclusive to splinter,
# I'm just overriding the default browser fixture settings
# If you just use selenium, no worries, just take note of the remote url and use 
# it wherever you define your selenium browser

@pytest.fixture(scope='session')
def splinter_webdriver():
    return 'remote'

@pytest.fixture(scope='session')
def splinter_remote_url():
    return 'http://selenium:4444/wd/hub'

Don't forget to set ALLOWED_HOSTS in your config file:

if env('USE_DOCKER') == 'yes':
    import socket

    ALLOWED_HOSTS = [socket.gethostbyname(socket.gethostname())]

# or just
ALLOWED_HOSTS = ['*']

Then just test away!

from django.urls import reverse


def test_site_loads(browser, test_server):
    browser.visit(test_server.url + reverse('admin:index'))

Answer 3

I have just specified host='web' for LiveServerTestCase . Here is my working solution.

test.py

from django.test import LiveServerTestCase
from selenium import webdriver
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities

class FunctionalTestCase(LiveServerTestCase):
    host = 'web'
    def setUp(self):
        self.browser = webdriver.Remote(
            command_executor="http://selenium:4444/wd/hub",
            desired_capabilities=DesiredCapabilities.FIREFOX
        )

    def test_user_registration(self):
        self.browser.get(self.live_server_url)
        self.assertIn('Django', self.browser.title)

    def tearDown(self):
        self.browser.close()

docker-compose.yml

version: '3'
services:
  db:
    image: postgres
  web:
    build: .
    ports: 
      - "8000:8000"
    depends_on:
      - db
      - selenium
  selenium:
    image: selenium/standalone-firefox

Remember you have to have to install the selenium in your docker image for this to work:

$ docker-compose exec web bash
> pip install selenium
...
> pip freeze > ../requirements.txt
> exit
$ ...

Answer 4

In my case, the "web" container runs only one command, which is bash -c "sleep infinity" .

Then, I start the whole stack with docker-compose up -d .

Then, I use docker-compose exec web bash -c "cd /usr/src/app && tox" , for example.

This way, my web host is accessible from selenium , always under the same name.

Using docker-compose run web ... generates new (predictable, but still) host name every single time.