Extend Function Behaviour with Optional Parameters in Automated E2E Scripts

Without breaking existing test scripts

In the article “Using Default Parameter Values in Automated E2E Test Scripts with Ruby,” I discussed how to leverage function default parameter values in E2E test scripts. Here, I will showcase a specific (and simple) technique for extending functions that my father taught me — one that is both practical and frequently used.

In E2E scripting, following Maintainable Automated Test Design, we define reusable helper functions and page functions (in POM).

These two functional test design patterns are applicable to nearly any programming language; here, I demonstrate them using the Ruby language.

1. Reusable helper functions

Example:

def login(username, password)
  driver.find_element(:id, "username").sendkeys(username)
  driver.find_element(:id, "password").sendkeys(password)
  driver.find_element(:input, "//input[@value='Sign in']").click
end

2. Page Functions (in page object model)

Example:

  it "User can enter passenger details" do
    sign_in("agileway", "testwise")

    flight_page = FlightPage.new(driver)
    flight_page.select_oneway_trip
    flight_page.select_from_city("Sydney")
    flight_page.select_to_city("New York")
    flight_page.click_continue

    passenger_page = PassengerPage.new(driver)
    passenger_page.enter_first_name("Bob")
    passenger_page.enter_last_name("Tester")
    passenger_page.click_next
    expect(driver.find_element(:name, "holder_name")["value"]).to eq("Bob Tester")
  end

Along the way, we often found the need to extend those functions. For instance, add checking “remember me” in the login function.

def login(username, password)
  driver.find_element(:id, "username").sendkeys(username)
  driver.find_element(:id, "password").sendkeys(password)
  driver.find_element(:input, "//input[@value='Sign in']").click
end

def login_with_remember_me(username, password)
  driver.find_element(:id, "username").sendkeys(username)
  driver.find_element(:id, "password").sendkeys(password)
  driver.find_element(:id, "remember_me").click # optional
  driver.find_element(:input, "//input[@value='Sign in']").click
end

The reasoning behind creating a separate login_with_remember_me function: keep the old login function unchanged, as it is used in many test scripts.

The above implementation is flawed because it violates the DRY (Don’t Repeat Yourself) principle, resulting in maintenance issues.

A good solution is to add an optional parameter to the login function.

def login(username, password, remember_me = false)
  driver.find_element(:id, "username").sendkeys(username)
  driver.find_element(:id, "password").sendkeys(password)
  if remember_me
    driver.find_element(:id, "remember_me").click
  end
  driver.find_element(:input, "//input[@value='Sign in']").click
end

Yes, the above works, but it’s not optimal. Why? Two reasons:

1. The test script is less readable.

login("agileway", "testwise") # old way, still works. ✓

# ...

login("agileway", "testwise", true) # check the remember me

The second one is not good, end users will puzzle, “What does true mean here?”

2. Hard to extend further.

Imagine the website now added two radio buttons for “customer login” and “staff login”. The test script may end up like below:

login("agileway", "testwise", false, true) # staff login, without remember me

It works, but is not good.

My father’s solution