Using Default Parameter Values in Automated E2E Test Scripts with Ruby

Using Ruby default parameter in your E2E test scripts can make your scripts more readable.

Below is an example of a typical user login test implemented using Selenium WebDriver in Ruby.

it "User Login OK" do
   driver.find_element(:id, "username").sendkeys("whenwise")
   driver.find_element(:id, "password").sendkeys("test01")
   driver.find_element(:input, "//input[@value='Sign in']").click
   #...
end

Obviously, we are going to use these three test steps often in other tests. Following the Maintainable Automated Test Design, make it a reusable function (by invoking a “Extract Function” refactoring, which TestWise can do).

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


it "User Login OK" do
  login("whenwise", "test01")
  #...
end

it "User Login OK failed with a wrong password" do
  login("whenwise", "tryluck")
  #...
end

it "Other User Login OK" do
  login("buildwise", "test01")
  #...
end

it "Another User Login OK" do
  login("testwise", "test01")
  #...
end

# ...

The script is now more readable and, more importantly, easier to maintain. Typically, I follow up with a “Move to Helper” refactor to make this function reusable across all test scripts.

Typically, the passwords for many test users are identical, often set to something like “test01”. Some testers may prefer the following test script style, as it enhances readability.

it "User Login OK" do
  login("whenwise")
  #...
end

it "Other User Login OK" do
  login("buildwise")
  #...
end

it "Another User Login OK" do
  login("testwise")
  #...
end

This is easy to achieve in Ruby: add a default value for the password parameter.

def login(username, password="test01")
  driver.find_element(:id, "username").sendkeys(username)
  driver.find_element(:id, "password").sendkeys(password)
  driver.find_element(:input, "//input[@value='Sign in']").click
end

This means the second argument, password, is optional. If not specified, it will use the default value: test01.

The following two uses of this login function are both OK: with one parameter and two parameters.

it "User Login OK" do
  login("whenwise")
  #...
end

it "User Login OK failed with a wrong password" do
  login("whenwise", "tryluck")
  #...
end

While the above example is simple, it showcases an important concept in E2E Test Automation: Improving the quality of test scripts without introducing breaking changes.

I will explain more in another (upcoming) article: “Extending Function Behaviour with Optional Parameters in Automated E2E Ruby Scripts”.

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Related reading:

• My book: “Web Test Automation in Action: Volume 1, Hands-On Exercises with Selenium WebDriver and Playwright”

• Why Ruby is the Best Scripting Language for End-to-End Test Automation?