Add AB test to request new Explore supermenu header from Static

Static has a new header that the GOV.UK Explore team want to AB test as part of their beta.

app/controllers/application_controller.rb

@@ -1,6 +1,7 @@
 class ApplicationController < ActionController::Base
   include Slimmer::Headers
   include Slimmer::Template
+  include ExploreMenuAbTestable
 
   rescue_from GdsApi::TimedOutException, with: :error_503
   rescue_from GdsApi::EndpointNotFound, with: :error_503
@@ -11,7 +12,10 @@ class ApplicationController < ActionController::Base
   rescue_from GdsApi::HTTPForbidden, with: :error_403
   rescue_from RecordNotFound, with: :cacheable_404
 
-  slimmer_template "gem_layout"
+  before_action :set_explore_menu_response
+  before_action :set_slimmer_template
+
+  helper_method :explore_menu_variant, :explore_menu_testable?
 
   if ENV["BASIC_AUTH_USERNAME"]
     http_basic_authenticate_with(
@@ -22,6 +26,14 @@ class ApplicationController < ActionController::Base
 
 protected
 
+  def set_slimmer_template
+    if explore_menu_testable?
+      slimmer_template "gem_layout_explore_header"
+    else
+      slimmer_template "gem_layout"
+    end
+  end
+
   def error_403
     error :forbidden
   end

app/controllers/concerns/explore_menu_ab_testable.rb

@@ -0,0 +1,26 @@
+module ExploreMenuAbTestable
+  CUSTOM_DIMENSION = 47
+
+  ALLOWED_VARIANTS = %w[A B Z].freeze
+
+  def explore_menu_test
+    @explore_menu_test ||= GovukAbTesting::AbTest.new(
+      "ExploreMenuAbTestable",
+      dimension: CUSTOM_DIMENSION,
+      allowed_variants: ALLOWED_VARIANTS,
+      control_variant: "Z",
+    )
+  end
+
+  def explore_menu_variant
+    explore_menu_test.requested_variant(request.headers)
+  end
+
+  def set_explore_menu_response
+    explore_menu_variant.configure_response(response) if explore_menu_testable?
+  end
+
+  def explore_menu_testable?
+    explore_menu_variant.variant?("B")
+  end
+end

app/views/calendar/bank_holidays.html.erb

@@ -1,5 +1,6 @@
 <% content_for :extra_headers do %>
   <%= @requested_variant.analytics_meta_tag.html_safe %>
+  <%= explore_menu_variant.analytics_meta_tag.html_safe if explore_menu_testable? %>
 <% end %>
 
 <%= render :partial => "calendar_head" %>

app/views/homepage/index.html.erb

@@ -1,6 +1,7 @@
 <% content_for :extra_headers do %>
 <link rel="canonical" href="<%= Frontend.govuk_website_root + root_path %>" />
 <meta name="description" content="GOV.UK - The place to find government services and information - Simpler, clearer, faster" />
+<%= explore_menu_variant.analytics_meta_tag.html_safe if explore_menu_testable? %>
 <% end %>
 <% content_for :title, "Welcome to GOV.UK" %>
 <% content_for :body_classes, "homepage" %>

test/functional/calendar_controller_test.rb

@@ -12,6 +12,17 @@ class CalendarControllerTest < ActionController::TestCase
       stub_content_store_has_item("/when-do-the-clocks-change")
     end
 
+    context "AB testing of Explore navigational super menu" do
+      should "request for Explore navigational super menu from slimmer" do
+        with_variant ExploreMenuAbTestable: "B" do
+          get :calendar, params: { scope: "bank-holidays" }
+
+          assert response.successful?
+          assert "core_layout_explore_header", assigns[:slimmer_template]
+        end
+      end
+    end
+
     context "HTML request (no format)" do
       should "load the calendar and show it" do
         get :calendar, params: { scope: "bank-holidays" }