Part 8: Using a base class

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Now you have multiple tests you are probably feeling pretty good about your progress. However there are other ways to improve code efficiency further — you may notice that you've so far had to include a setUp() and a tearDown() method in each test file, going by the current constructs we've seen in this series. If you have several dozen tests then that’s a lot of code duplication! In this article we'll look at how to put the setUp()/tearDown() code common to all tests into a TestBase class, which can then be imported into each individual test file.

To start with, create a new file called, in the same directory as your existing test cases.

Next, move your important statements that relate to the common setup (unittest, Marionette and time) into the file, along with a TestBase class containing the setUp() and tearDown() methods, and associated common helper functions (such as unlock_screen()). The file should look something like this:

import time
import unittest
from marionette import Marionette

class TestBase(unittest.TestCase):

    def unlock_screen(self):

    def kill_all(self):
             // Kills all running apps, except the homescreen.
             function killAll() {
               let manager = window.wrappedJSObject.AppWindowManager;

               let apps = manager.getApps();
               for (let id in apps) {
                 let origin = apps[id].origin;
                 if (origin.indexOf('verticalhome') == -1) {
             // return true so execute_async_script knows the script is complete

    def setUp(self):
         # Create the client for this session. Assuming you're using the default port on a Marionette instance running locally
        self.marionette = Marionette()

        # Unlock the screen

        # kill all open apps

        # Switch context to the homescreen iframe and tap on the contacts icon
        home_frame = self.marionette.find_element('css selector', 'div.homescreen iframe')

    def tearDown(self):
        # Close the Marionette session now that the test is finished

Updating your test files

With your file created, you need to import TestBase into your test files, and the test classes need to be changed to extend the TestBase class:

import unittest
from marionette import Wait
from marionette import By
from test_base import TestBase
class TestContacts(TestBase):

    def test(self):
        # Tests in here
if __name__ == '__main__':

Try running your test file again.

It may not look like much now but when you have dozens or hundreds of tests this really saves a lot of duplicate code.

Document Tags and Contributors

 Contributors to this page: chrisdavidmills, zac_c, Tingyu
 Last updated by: chrisdavidmills,