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Test Case Desing Approach: imperative vs declarative

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Test case design is the most important part of test automation since it is the starting point of the automation code. Writing effective and efficient test case can make your code more stable and more successful. For BDD approach, the feature files hold the test cases or scenarios and these scenarios are derived by depending on the acceptance criterias written in the stories. Therefore the feature files should cover all the acceptance criteria plus some more test cases produced from exploratory testing. 
The approach for the writing your scenarios can be imperative or declarative or mix of both. In this post want to explain my understanding from the design approaches and their prons and cons. 

For dictionary meaning of imperative is giving authoritative command,  and declarative is taking the form of a simple statement according to the Oxford dictionary. My understanding from this explanation is that you can say "do this ..." as an imperative way or you can say "this is like ..." as an declarative way. Check this funny but declarative examples from here. Lets use these basic information for our field as software engineer and derive test scenarios:

An imperative examples(How):
Scenario: User should see greeting message for succesfull registeration
When user enters "Name" as "John"
And user enters "Surname" as "Doe"
And user enters "Email" as "johndoe@testrisk.com"
And user enters "Password" as "Pass123456"
And user selects gender as "Male"
And user selects "Birtday" as "1990"
And user checks terms and conditions
And user clicks at "Register" button
Then user should see "Welcome" pop-up
view raw imperative.feature hosted with ❤ by GitHub

correspondingly step definition should like the following:
When(/^user enters "(.*?)" as "(.*?)"$/) do |field, text|
enter_text IDs.items[field] text
end
When(/^user selects gender as "(.*?)"$/) do |field|
touch IDs.items[field]
end
When(/^user selects "(.*?)" as "(.*?)"$/) do |list, value|
select_from_list IDs.items[list] value
end
When(/^user checks terms and conditions$/) do
touch IDs.items["Terms and Condition"]
end
When(/^user clicks at "(.*?)" button$/) do |button|
touch IDs.items[button]
end
Then(/^user should see "(.*?)" pop\-up$/) do |popup|
expect(element_exists(IDs.items[popup]).to be true)
end
view raw imp_step_definiton.rb hosted with ❤ by GitHub


An declarative examples(What):
Scenario: User should see greeting message for succesfull registration
When user submits the registration form with valid user information
Then user should see "Welcome" pop-up
view raw declarative.feature hosted with ❤ by GitHub

correspondingly step definition should like the following:
When(/^user submits the registration form with valid user information$/) do
enter_text IDs.items["Name"], "John"
enter_text IDs.items["Surname"], "Doe"
enter_text IDs.items["Email"], "johdoe@testrisk.com"
enter_text IDs.items["Password"], "Password1213"
touch IDs.items["Male"]
select_from_list IDs.items["Birt"], "1990"
touch IDs.items["Terms and Condition"]
touch IDs.items["Register"]
end
Then(/^user should see "(.*?)" pop\-up$/) do |popup|
expect(element_exists(IDs.items[popup]).to be true)
end
view raw dec_step_definition.rb hosted with ❤ by GitHub


Prons and cons of imperative approach:
  • More detail about steps
  • A kind of micro (steps) management of test cases
  • More feed backs when failures occur
  • You can use the features of Cucumber more efficiently
  • Gives more information to consumer for whole steps
  • You can produce more reusable steps
    •
  • Not suitable for generalisation
  • More documentary work
  • A bit confusing if you are checking the result of a long list  
    •

    Prons and cons of declarative approach:
  • Good for cross-platform testing
  • Good for generalization
  • Good if we are interested in summary of test case results
  • Group of actions, easy to manage
    •
  • More automation code
  • Not good for reusable steps
    •

    As we can see from the examples difference is related to abstraction level which the imperative approach gives more detail about what is doing for each steps. However this is not the case, important part is that declarative approach explains a case in a general way so it can be suitable for similar product. This could help you if you are writing test cases for different platform of same application. For example, if you are testing a log in form for both iOs and Android, and for both phone and tablet you can see some differences because of the standardisation of the platforms and device specific extra features. Therefore, writing a declarative test case and handling these kind of differences in automation code not in test step can make your .feature files more help full. I think deciding which approach to use is depending on your consumer needs and your automation framework. Best practice should be include both approach for different cases.

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