Creating page objects with a dynamic page_url

Problem

There was a StackOverflow question today about visiting dynamically generated urls with the page object gem.

For example, the url of the page to view a StackOverflow user is in the form http://stackoverflow.com/users/1200545 where the id portion, “1200545”, is the specific user you want to view. You could create a page object to visit/interact with this page.

class StackOverflowUserPage
  include PageObject
  
  page_url "http://stackoverflow.com/users/1200545"
end

visit StackOverflowUserPage do |page|
  # Do stuff
end

But what happens when you have multiple users? This page_url is specific to the one user. Each user would have a different id and therefore a different page_url. You could create a page object for each user, but that is a lot of duplication. As well, you might not know the required id before hand – ie it might get dynamically generated during your test.

Solution

To solve this, the page object gem allows you to create/visit dynamically generated urls. This is done by using ERB to include values from a params hash.

In the page_url, you can replace the hard-coded id value with <%=params[:id]%>. The url will be evaluated with ERB, which basically inserts the value returned from the code between the “<%=” and “%>”. The concept is similar to string interpolation.

class StackOverflowUserPage
  include PageObject
  
  page_url "http://stackoverflow.com/users/<%=params[:id]%>"
end

You can then visit the page by specifying the dymamic portions of the url. This is done by passing in an extra :using_params hash.

visit StackOverflowUserPage, :using_params => {:id => '1200545'} do |page|
  # Do stuff with specific user
end

If you want to add default parameter values, you can add a @params hash to the page object. For example, say by default, we want to view our user 1200545. Then we can change the page object to:

class StackOverflowUserPage
  include PageObject
  
  @params = {:id => '1200545'}
  page_url "http://stackoverflow.com/users/<%=params[:id]%>"
end

Then we can visit our default user without specifying the params:

visit StackOverflowUserPage do |page|
  # Do stuff with default user
end

For a different user, we can still specify their specific id:

visit StackOverflowUserPage, :using_params => {:id => '9999999'} do |page|
  # Do stuff with specific user
end

Note

If part of the url needs to be dynamic but is known ahead of time and does not change, you can use string interpolation instead of ERB.

For example, say we have 2 environments to test against – http://stagestackoverflow.com and http://labstackoverflow.com. The environment is always known ahead of time and does not change during the life of the page object class.

In this case, it is easier to use string interpolation rather than ERB.

$environment = 'stage' # or 'lab'

class StackOverflowUserPage
  include PageObject
  
  page_url "http://#{$environment}stackoverflow.com/users/1200545"
end

We cannot use this approach for the dynamic id portion as the string interpolation of the page_url is evaluated (ie becomes set in stone) when the page object class is evaluated, which is before we call the visit method (ie before we know what id we want to visit).