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Frontend Testing With Selenium

This file contains a description about necessary steps to start testing with selenium as well as some remarks about setting up new tests.

Required Selenium setup

Note that this setup has been tested and used exclusively with Python 3.6. Using Python 2 is not encouraged.

  • Download the Selenium server (selenium-server-standalone-[version].jar) from the selenium page

  • Information on how to get the webdrivers for Chrome and Firefox ("Geckodriver") can also be found on the page above. Since the location of these drivers has changed in the past, selenium does not link directly. The latest locations for driver downloads at this point where

  • Make sure the server jar and the webdrivers are in a location that is available via the PATH environmental variable.

  • Install the required python dependencies; pip install selenium pytest.

  • Open a python shell and run the following code to check if the webdrivers work

    from selenium import webdriver
cdriver = webdriver.Chrome()
fdriver = webdriver.Firefox()

  • If any problems arise at this point, check whether the driver that was downloaded supports the actually installed corresponding browser.

Preliminary requirements

Test database setup

  • Make sure that activator test has been run; all frontend tests depend on the the h2 test database content which is created when the backend tests are executed.
  • Make sure GCA-Web is running locally at the default port 9000 using activator run.

Selenium preparation

To allow parallel and cross browser testing and even giving the possibility of testing with different operating systems and on different machines, we next set up selenium grid using the selenium server jar mentioned above.

The hub can be started by opening a terminal, changing to the selenium folder and then typing in the following command (use your current version of the jar):

java -jar selenium-server-standalone-3.141.59.jar -role hub

Leave the terminal running, open another terminal, navigate to the directory and add a node to the hub:

java -jar selenium-server-standalone-3.141.59.jar -role node

If you now visit http://localhost:4444/grid/console you can see the node registered and which browsers are available on each of them. You can set the port, the browser running on the node and various other parameters. It is also possible now to register nodes from different machines, given you know the IP of the hub, by expanding the command above to

java -jar selenium-server-standalone-3.141.59.jar -role node -hub http://$IP of hub$:4444/grid/register

You can also add more nodes via the same command, speeding up the run time of the tests, as they will get distributed over these nodes by pytest.

Running the tests

After the preparation steps above, open another terminal and navigate to the GCA-Web test/frontend folder. The tests can be run by python -m pytest or python -m pytest [testfile].

Using the pytest-xdist module, parallel testing is possible, decreasing the overall run time of the tests. Please note that pytest-xdist is an extension plugin, not part of the pytest distribution and needs to be installed separately. Try to keep the number of open browser windows around 4-6, otherwise the usage of memory space will increase times again.

Potential issues

  • Make sure that you browser and corresponding browser driver versions are compatible. This is likely the cause behind errors of type

      selenium.common.exceptions.SessionNotCreatedException: Message: 
    Unable to create new service: ChromeDriverService

  • If you obtain a connection error in the browser, be sure that no proxy server is set in your browser. This might also cause the browser to load slowly.

Creating new tests

There are some issues you can encounter, when adding tests.

  • Using pytest and fixtures, the unittest.TestCase class does not work.

  • For each class, you can add another fixture in the conftest.py file.

  • Driver set-up and starting at the login page is already contained in the maximize_login(request) function.

  • Working with the selenium standalone server, set up new drivers via

    driver = webdriver.Remote(
            command_executor="http://" + Cookies.get_host_ip() + ":4444/wd/hub",
            desired_capabilities={'browserName': '$driver_name$', 'javascriptEnabled': True}
        )

  • In case you want to run the tests without the standalone server, replace the remote webdriver. You only need to do this once in the maximize_login(request) function.

    driver = webdriver.Firefox()
# or
driver = webdriver.Chrome()

  • If you want to add cookies, first open up another page, load the cookies and the go to the desired page or reload. Compare with the already used set up functions in the conftest.py file. An issue with selenium is that using localhost in URLs can cause problems with, e.g. loading cookies. As a workaround, always use the Cookies.get_host_ip().

  • With most browser drivers, elements searched for by functions of the type driver.get_element_by_*() will be found automatically, even if they're outside of the section currently viewed on the screen. In Firefox (Geckodriver) an error will be returned in such cases. It is important for Firefox to always navigate/scroll to the element before examination by using move_to_element_by_*(). For often used actions like the click(), send_keys() or get_attribute() functions including this are predefined in the conftest.py file.

  • Generally tests run stable. In some incidences a test might fail due to local issues, repeating the test might work then. To avoid such problems, it is useful to include the following code snipped after processes that are expected to need some time to execute, e.g. when saving a form or loading a page or modal.

    WebDriverWait(driver, 30).until(
    # insert expected condition, e.g.
    EC.presence_of_element_located((By.XPATH, ''))
)

References and links