WIP - add AB test for /find-utr-number

app/controllers/content_items_controller.rb

@@ -24,6 +24,21 @@ class ContentItemsController < ApplicationController
   def show
     load_content_item
 
+    # TEMPORARY (author: richard.towers, expected end date: November 30 2023)
+    # Content specific AB test for the Find your UTR number page
+    if @content_item.base_path == "/find-utr-number"
+      ab_test = GovukAbTesting::AbTest.new(
+        "find_utr_number_video_links",
+        dimension: 300, # TODO: which dimension should we use?
+        allowed_variants: %w[HelpText VideoLink],
+        control_variant: "HelpText",
+      )
+      @requested_variant = ab_test.requested_variant(request.headers)
+      @requested_variant.configure_response(response)
+      @content_item = AnswerFindYourUtrPresenter.new(@content_item, @requested_variant.variant_name)
+    end
+    # /TEMPORARY
+
     set_expiry
 
     if is_service_manual?

app/presenters/answer_find_your_utr_presenter.rb

@@ -0,0 +1,32 @@
+# TEMPORARY (author: richard.towers, expected end date: November 30 2023)
+# Content specific AB test for the Find your UTR number page
+class AnswerFindYourUtrPresenter < AnswerPresenter
+  def initialize(parent_presenter, ab_test_variant)
+    super(
+      parent_presenter.content_item,
+      parent_presenter.requested_path,
+      parent_presenter.view_context
+    )
+    @ab_test_variant = ab_test_variant
+  end
+
+  def body
+    result = super
+    if @ab_test_variant == "VideoLink"
+      # NOTE: this is a fragile way of doing an AB test on content.
+      #
+      # Any change to the base content, or to the way the content is rendered
+      # could potentially break the B variant of the test, and result in both
+      # variants being the same.
+      # We're aware of this risk, and we're going to be careful in this one off
+      # situation. This is not a sustainable way of doing AB tests in the
+      # future.
+      result.sub(
+        /<li>\s*in\ the\s+<a\ href="[^"]*"><abbr\ title="[^"]+">HMRC<\/abbr>\s+app<\/a>/,
+        '<li>in the <a href="https://www.gov.uk/guidance/download-the-hmrc-app"><abbr title="HM Revenue and Customs">HMRC</abbr> app</a> - watch a <a href="https://www.youtube.com/watch?v=LXw9ily9rTo">video about finding your UTR number in the app</a>',
+      )
+    else
+      result
+    end
+  end
+end