Behavior Driver Development is growing in popularity, and performing BDD with Python is no exception. Behave is a popular BDD framework for performing tests, and, because Behave is built on Python's Selenium language bindings, performing Behavioural Driven testing on CBT is easy. We'll walk your through getting started here.
Get set up
To get started, we will need to ensure that Behave is installed. The easiest means of doing so is with PIP:
Alternatively you can read installation documenation on the Behave website.
We also need to install Requests so we can perform interactions with our API like taking a snapshot and setting the score:
Lastly, we will need to install Selenium:
Write tests
Once that is complete, we are ready to start writing our first test with Behave. Tests start with writing "Feature" files that use plain english to describe the steps of your test. Features use keywords to form the actual steps being taken in the test:
- Given we put the system in a known state before the user (or external system) starts interacting with the system (in the When steps). Avoid talking about user interaction in givens.
- When we take key actions the user (or external system) performs. This is the interaction with your system which should (or perhaps should not) cause some state to change.
- Then we observe outcomes.
Create a new directory with a single file we will call 'Example.feature'. You can then copy the following feature into your feature file:
Scenario: Test Login
Given I go to my login form
Then the title should be "Login Form - CrossBrowserTesting.com"
When I enter my credentials
When I click login
Then I should see the login message
Next, we will need to modify the environment we are testing on so we can perform our test in the cloud. Add another file to your directory called environment.py, and copy the following script into it:
Python
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
import requests
import subprocess
username = "[email protected]"# change this to the username associated with your account
authkey = "yourauthkey"# change this the authkey found on the 'Manage Account' section of our site
def before_feature(context, feature):
caps = {}
caps['name'] = 'Behave Example'
caps['build'] = '1.0'
caps['browserName'] = "Chrome"# pulls the latest version of Chrome by default
caps['platform'] = "Windows 10"# to specify a version, add caps['version'] = "desired version"
caps['screen_resolution'] = '1366x768'
caps['record_video'] = 'true'
caps['record_network'] = 'false'
caps['take_snapshot'] = 'true'
context.api_session = requests.Session()
context.api_session.auth = (username, authkey)
# cmd = "cbt_tunnels --username " + username + " --authkey " + authkey + " --ready tunnel_ready asadmin"
# context.tunnel_proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, shell=True)
context.driver = webdriver.Remote(
desired_capabilities=caps,
command_executor="http://%s:%[email protected]:80/wd/hub"%(username, authkey)
)
def after_feature(context, feature):
context.driver.quit()
# subprocess.Popen.terminate(context.tunnel_proc)
As you can see from our example, we are creating a Remote WebDriver that points to our hub. You can alternatively start a local connection so you can access locally hosted content. Just ensure that you have installed cbt_tunnels and then uncomment out the lines of code necessary for running the subprocess.
Now its time to actually define the steps from our Example.feature file in code. Create a new directory within your current one called Steps. This is where Behave will initially look for the code for your tests. Within that directory, create a file called login_example.py, and copy to following code into that file:
Python
def go_to_login_form(context):
context.driver.get('http://crossbrowsertesting.github.io/login-form.html')
@then('the title should be {text}')
def verify_title(context, text):
title = context.driver.title
try:
assert "Login Form - CrossBrowserTesting.com" == title
except AssertionError as e:
set_score(context, 'fail')
@when('I enter my credentials')
def enter_credentials(context):
context.driver.find_element_by_id('username').send_keys('[email protected]')
context.driver.find_element_by_id('password').send_keys('test123')
@when('I click login')
def click_login(context):
context.driver.find_element_by_xpath('/html/body/div/div/div/div/form/div[3]/button').click()
@then('I should see the login message')
def see_login_message(context):
context.driver.implicitly_wait(10)
elem = context.driver.find_element_by_xpath('//*[@id=\"logged-in-message\"]/h2')
welcomeText = elem.text
try:
assert "Welcome [email protected]" == welcomeText
set_score(context, 'pass')
except AssertionError as e:
set_score(context, 'fail')
def set_score(context, test_result):
context.api_session.put('https://crossbrowsertesting.com/api/v3/selenium/' + context.driver.session_id,
data={'action':'set_score', 'score': test_result})
You should note that we use, the Given-When-Then prefixes before every corresponding function. Steps are narrowed down to individual functions and the whole feature acts as a single unit test. At the end we set the score to the final value of our score variable, and our test is complete.
This is just the beginning of what you can do with Behave and Selenium! There is really no limits to what is possible with Selenium, and Behave makes it much easier, especially if you are working with QA's that are not programmers.
For examples and source code to this tutorial, check out our Behave GitHub Repository
If you have any trouble getting setup, do not hesitate to reach out to us. We are happy to help.
See Also
Test Frameworks and Tools
About Selenium Testing
Selenium and Python
Lettuce