Merge pull request #2711 from alphagov/gtm_component

Conditionally add the GTM component

Gemfile

@@ -30,6 +30,7 @@ group :development, :test do
 end
 
 group :test do
+  gem "climate_control"
   gem "govuk-content-schema-test-helpers"
   gem "jasmine-core"
   gem "minitest"

Gemfile.lock

@@ -82,6 +82,7 @@ GEM
       regexp_parser (>= 1.5, < 3.0)
       xpath (~> 3.2)
     childprocess (3.0.0)
+    climate_control (1.0.1)
     coderay (1.1.3)
     concurrent-ruby (1.1.9)
     crack (0.4.4)
@@ -349,6 +350,7 @@ DEPENDENCIES
   actionpack-page_caching
   better_errors
   binding_of_caller
+  climate_control
   gds-api-adapters
   govuk-content-schema-test-helpers
   govuk_app_config

app/views/root/_gem_base.html.erb

@@ -32,6 +32,16 @@
   global_bar << global_banner if global_banner
 %>
 
+<% content_for :head do %>
+  <% if ENV["GOOGLE_TAG_MANAGER_ID"] %>
+     <%= render "govuk_publishing_components/components/google_tag_manager_script", {
+       gtm_id: ENV["GOOGLE_TAG_MANAGER_ID"],
+       gtm_auth: ENV["GOOGLE_TAG_MANAGER_AUTH"],
+       gtm_preview: ENV["GOOGLE_TAG_MANAGER_PREVIEW"]
+     } %>
+  <% end %>
+<% end %>
+
 <%= render "govuk_publishing_components/components/layout_for_public", {
   account_nav_location: account_nav_location,
   draft_watermark: draft_environment,

test/integration/google_tag_manager_component_test.rb

@@ -0,0 +1,19 @@
+require "integration_test_helper"
+
+class GoogleTagManagerComponentTest < ActionDispatch::IntegrationTest
+  context "GTM environment variables are present" do
+    should "render the GTM component on the gem_base template" do
+      ClimateControl.modify GOOGLE_TAG_MANAGER_ID: "a-nice-id" do
+        visit "/templates/gem_layout.html.erb"
+        assert_match "https://www.googletagmanager.com/gtm.js", page.body
+      end
+    end
+  end
+
+  context "GTM environment variables are absent" do
+    should "not render the GTM component on the gem_base template" do
+      visit "/templates/gem_layout.html.erb"
+      assert_no_match "https://www.googletagmanager.com/gtm.js", page.body
+    end
+  end
+end