Ruby on Rails

Once I completed Michael Hartl's tutorial, I packed my homepage in a partial and called it _social_layer.html.erb
Then I inserted this partial in my new homepage and proceeded to develop my application.
Therefore, an extract of application's new homepage looks like as follows:

<!-- Tab panes -->
<div class="tab-content">

    <div role="tabpanel" class="tab-pane active" id="social-layer">
        <%= render 'static_pages/social_layer' %>
    </div>

    <div role="tabpanel" class="tab-pane" id="atp-team">
        <% if @atp_tournaments.any? %>
        <ul>
            <% @atp_tournaments.each do |tournament| %>
                <li> <%= tournament.name %>: <%= tournament.category %> </li>
            <% end %>
        </ul>
        <% end %>
    </div>
    ...

As you can see this page is divided in sections or tabs, each one containing the respective code.
I inserted Michael Hartl's tutorial in the first tab.

There are two versions for my homepage, one dedicated to freshly registered users and one for users who have completed a certain selection.
I called these two pages _non_gamers_home.html.erb and _gamers_home.html.erb
The code above belongs to the version of the homepage dedicated to gamers (_gamers_home.html.erb)
So my home.html.erb file is made up of if/else statements and contains these two partials.

The problem is that If I run the integration test dedicated to the microposts interface (the _social_layer.html.erb partial), the test fails because all instance variables in my homepage that do not belong to the social layer partial (the first one is @atp_tournaments as you can see in the above code) result nil.

I do not understand why this test fails.
All these instance variables belong to the controller that controls the home page (static_pages_controller.rb) and should be loaded by the test.
If I change these variables with their explicit value in the above code the test passes.