5 Tips Of GUI Tests With Python + Selenium

1. Use Docker To Setup Selenium headless Environments

Setup GUI testkit takes effort. Especially in old days! Ever heard of something like Xvfb[1], Xephyr, PyVirtualDisplay[2], etc.

Too much information, isn’t it? It will blow your mind. Not to mention the maintenance effort. And yes, the trouble shooting!

#1 Tip: Use Docker To Setup TestKit.

Check dockerfile in github. Follow @dennyzhang

# Start container
docker run -d --restart=always \
    -v /tmp/screenshot:/tmp/screenshot \
    -h selenium --name selenium denny/python-selenium:v1

# Run A Sample Test.
# With customized test scripts, you can do more!
docker exec selenium \
   python /home/seluser/selenium_load_page.py \
   --page_url https://www.dennyzhang.com --should_save_screenshot

# Check Screenshot
ls -lth /tmp/screenshot

With above simple command, your remote Xvfb server would be up and running now.

If it had crashed, your container will crash too. Consequently it will be restarted automatically. Beautiful, isn’t it?

contact$dennyzhang.com docker exec -it selenium ps -ef | grep -i xvfb
seluser     12     1  0 Sep04 ?        00:00:00 /bin/sh /usr/bin/xvfb-run -n 99
seluser     23    12  0 Sep04 ?        00:00:00 Xvfb :99 -screen 0 1360x1020x24

2. Deal with async loading for javascripts and css

In web programming, async loading is quite common. Especially with the technology of nodejs. So before we check UI functionalities, we need to wait until elements to be shown.[3]

from selenium import webdriver

driver = webdriver.Firefox()
driver.implicitly_wait(10) # seconds
driver.get("http://somedomain/url_that_delays_loading")
myDynamicElement = driver.find_element_by_id("myDynamicElement")

3. Raise Alerts, If Page Load Is Too Slow

Apparently the first priority is making sure the major functionalities work.

But also remember to watch out the slowness. This helps people to detect the performance issues.

import time

print("Open page: %s" % (page_url))
start_clock = time.clock()

gui_login_webpage(driver, page_url, username, password)

end_clock = time.clock()
elapsed_seconds = ((end_clock - start_clock) * 1000)
is_ok = True
if elapsed_seconds > max_load_seconds:
    print("ERROR: page load is too slow. It took %s seconds, more than %d seconds." \
          % ("{:.2f}".format(elapsed_seconds), max_load_seconds))
    is_ok = False
else:
    print("Page load took: %s seconds." % ("{:.2f}".format(elapsed_seconds)))

4. Raise Alerts, If Any 5XX or 4XX Errors Are Detected.

One URL request will launch lots of http sub-requests. If any requests run into issues, we need to notify developers.

e.g:

IGNORE_ERROR_LIST = ["favicon.ico"]

all_warnings = driver.get_log('browser')
critical_errors = []
for warning in all_warnings:
    if warning['level'] == 'SEVERE':
        has_error = True
        for ignore_err in IGNORE_ERROR_LIST:
            if ignore_err in warning['message']:
                has_error = False
                break
        if has_error is True:
            critical_errors.append(warning)

5. Wrap GUI Test As Jenkins Jobs

People only accept solutions which are easy to use. So let’s use jenkins to achieve visualOps.

Quick Python Selenium CheatSheet [4]