Wednesday, February 19, 2014

Page Objects are not enough

The Page Object design pattern is one of the most popular patterns in test automation just because it promotes test maintenance and unifies the way QA teams work. As the pattern dictates, a page object is the representation of an html page using objects. The objects contain the html element addresses (Xpath, Css or DOM) and the user actions on them as methods (press, input, select, etc.).

Although the page objects pattern is widely accepted, our work experience showed that it is inadequate in fully describing an html page because it lacks the ability to represent the business logic of the page. In order to solve this problem we use a complimentary entity to the page object, the business object.

The business object is a class containing the business logic behind the page. An example of html page business logic is the validation of the mandatory fields of a form. The page object by its definition could not contain the aforementioned logic it can only carry the info that pressing the submitting button an error is raised without reasoning. The business object compliments the page object in having a method for trying to submit a form without the mandatory fields completed and an error is raised. The complimenting nature of the business object stands because the business objects uses the page object’s methods to assemble the logic thus its methods are a collection of page object methods.

The breakthrough of this approach in the representation of the html page is that it keeps a clear separation of the logic from the html elements introducing an abstraction layer for the business object thus separating future changes in the page logic from its locators. In addition it may introduce reusability (a business object may exist in more than one pages hence page objects). Using the previous example a possible subtraction of a mandatory field does not affect the page object only the business one thus the change is marked in a single place.

In a later post I will try to expand on how to implement our business objects and what we do in special cases such as repeating pages with in the software under test.