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Test Case Desing Approach: imperative vs declarative

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):

correspondingly step definition should like the following:

An declarative examples(What):

correspondingly step definition should like the following:

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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