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Sunday, September 25, 2016

When page object returns more than one type of page object

If have have been working with test automation then you would have probably heard of page objects. In a gist, page object provides clear separation of responsibility between who is responsible for testing (test classes) and who is responsible for services provided page (page classes). Page objects are known to return objects of same page when control retains on same page or another page object when operation on one page return object of another page. For example typing in a text box would keep control on same page (hence same page object) but submitting a form with valid data would most probably load a new page (hence a new page object).

But what if return type of Page Object is not fixed. For example for A/B variations, user may be directed to one of many possible variation of a page. Hence the resulting page is a page object but you don’t know for sure which age object. This is where java generics comes for rescue, and to be more specific generic methods.

Before delving into generic page object let’s see an example of generic method. If you have not worked with generic then java generic video tutorial will come handy.
Following example is a modified version of generic method. Let’s assume that we want to add a String element to given collection and return the modified collection. This could like as -

public Collection<String> addAndReturn(String element, Collection<String> collection) {
  return collection;

But what if requirements change and we need to add Integer object to collection. Would we write another method which takes Integer argument? What if we need another method which takes a custom Object, would we write another method which takes our custom Object argument? The requirements are endless. This is when generic methods helps us achieving code reusability. We can write one generic method which takes argument of any type <T>, add it to a given collection of objects of type <T> and return the collection -

public <T> Collection<T> addAndReturn(T element, Collection<T> collection) {
  return collection;

Herein <T> before the return type Collection<T> of method specifies a generic type. Notice that T is also the type of the element argument (T element) and collection argument (Collection<T> collection) of method. Now we can use this method to addAndReturn collection we want. The actual type of T is determined by the caller invoking addAndReturn method -

// add string to collection and return collection
Collection<String> stringCollection = new ArrayList<String>(Arrays.asList("a", "b","c"));
String string = "d";
System.out.println(addAndReturn(string, stringCollection));

// add int to collection and return collection
Collection<Integer> integerCollection = new ArrayList<Integer>(Arrays.asList(1, 2, 3));
int i = 4;
System.out.println(addAndReturn(i, integerCollection));

The concept of generic method can be applied to page object method as well when page object method may return a different page object -

public static <T extends PageObject> T getNewABPage() throws Exception {;
  return (T) new PageObject();

Herein <T extends PageObject> is the generic type, which is PageObject type itself or any type which extends PageObject class in stf. You can either extend the PageObject or use object of your choice. Exact page type of page object can be derived either in test method or another page object which calls the generic page object method -

PageObject pageObject = getNewABPage();
// logic to determine exact type of page object, for ex using page title or
// element on page
// Once we know the exact page object type then down cast it to the required page object to carry out operation on required page object
((SendFeedbackPage)pageObject).enterFeedback("positive feedback");

Another example of generic page object method is when page object method is accessible from multiple pages but returns the instance of same page object on which it is called -

public static <T extends PageObject> T getSettingsPopup(T type) {;
  return type;

And now any page can invoke settings popup and call the required operations on it

LoggedInUserHomePage loggedInUserHomePage = new LoggedInUserHomePage();

Can you think of more use cases when generic page object is useful ?
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