How Django get the live_server_url?

Question

I learned Django functional test from the TDD with Python and adjust to my project.

My FT is really simple, check the title of url.

I use live_server_url to test by selenium. But it goes to another port number(56458), not 8000. (When I follow the book, it wasn't)

$ python manage.py runserver &
...
Starting development server at http://127.0.0.1:8000/
...
$ python manage.py test functional_test
...
http://localhost:56458
E
======================================================================
...

My functional_tests/tests.py is :

from django.test import LiveServerTestCase

from selenium import webdriver
from selenium.webdriver.common.keys import Keys
from selenium.common.exceptions import WebDriverException

from time import time, sleep


class NewVistorTest(LiveServerTestCase):

    def setUp(self):
        self.browser = webdriver.Firefox()
        self.browser.implicitly_wait(3)


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

    def test_render_a_list_of_candiates_in_home(self):
        self.browser.get(self.live_server_url)
        h1_text = self.browser.find_element_by_tag_name('h1').text

        self.assertEqual(self.browser.title, 'Voting Dapp')
        self.assertEqual(h1_text, 'A Simple Voting Application')

Doc says:

The live server listens on localhost and binds to port 0 which uses a free port assigned by the operating system. The server’s URL can be accessed with self.live_server_url during the tests.

So I try to look listening ports(I think I'm immature for this part):

$ netstat | grep LISTEN
$ # nothing printed!

Answer 1

You use a LiveServerTestCase. It launches a Django server for you. No need to start a server like you did in the previous chapter.

LiveServerTestCase does basically the same as TransactionTestCase with one extra feature: it launches a live Django server in the background on setup, and shuts it down on teardown. This allows the use of automated test clients other than the Django dummy client such as, for example, the Selenium client, to execute a series of functional tests inside a browser and simulate a real user’s actions.

https://docs.djangoproject.com/en/2.0/topics/testing/tools/#django.test.LiveServerTestCase

So it is expected that your test server has some other port than the development server. Also the test server is an empty project with an empty db. So your test needs to create the needed content before you execute the actual test case.

Alternatively you can point to tests to some other environment with --liveserver LIVESERVER. See python manage.py test -h.

I think it is wrong to test against the development server as this data can be altered (manually and by previous tests) and therefore is not reproducible. I believe tests should be entirely self contained, such that it can be run either in isolation or in arbitrary combination with any number of other test cases.