Give a real application level example to clarify the concept of Driver and Stub?

Consider an application with business flow as below:

Login Page (On successful login) ->Home Page (Contact Us link at the footer of home page) → Clicking on Contact Us → Contact us page should open.

Now let’s assume we have to validate the Home page and in order to completely test its feature we should test its dependent functionalities with Login and Contact Us page as well.

However, both login and Contact Us page is still not developed. So, in this scenario we would need the assistance of both Driver and Stub to completely validate the Home page features and working.

So, let’s define the flow:

Here we find that, Home and Login page are associated in accordance with Bottom Up approach and hence the Login page would be replaced with dummy code called Driver and Home and Contact Us page are associated with Top Down approach and hence the Contact Us page would be replaced by dummy code called Stub.