Add some unit tests for this

app/controllers/application_controller.rb

@@ -1,6 +1,4 @@
 class ApplicationController < ActionController::Base
-  default_form_builder GOVUKDesignSystemFormBuilder::FormBuilder
-
   def render_not_found
     render "errors/not_found", status: :not_found
   end

config/initializers/default_form_builder.rb

@@ -0,0 +1 @@
+Rails.application.config.action_view.default_form_builder = GOVUKDesignSystemFormBuilder::FormBuilder

spec/views/form/page_view_spec.rb

@@ -0,0 +1,74 @@
+require "rails_helper"
+require_relative "../../request_helper"
+
+RSpec.describe "form/page" do
+
+  before do
+    RequestHelper.stub_http_requests
+  end
+
+  let(:case_log) { FactoryBot.create(:case_log, :in_progress) }
+  let(:form) { case_log.form }
+  let(:subsection) { form.get_subsection("income_and_benefits") }
+  let(:page) { form.get_page("net_income") }
+  let(:question) { page.questions.find { |q| q.id == "earnings" } }
+
+  def assign_attributes(object, attrs)
+    attrs.each_pair do |attr, value|
+      object.public_send("#{attr}=", value)
+    end
+  end
+
+  context "given a question with extra guidance" do
+    let(:expected_guidance) { /What counts as income?/ }
+    before do
+      assign(:case_log, case_log)
+      assign(:page, page)
+      assign(:subsection, subsection)
+      assign_attributes(question, attribs)
+      render
+    end
+
+    context "with radio type" do
+      let(:attribs) { { type: "radio", answer_options: {"1": "A", "2": "B"} } }
+      it "renders the guidance partial for radio questions" do
+        expect(rendered).to match(expected_guidance)
+      end
+    end
+
+    context "with text type" do
+      let(:attribs) { { type: "text", answer_options: nil } }
+      it "renders the guidance partial for text questions" do
+        expect(rendered).to match(expected_guidance)
+      end
+    end
+
+    context "with numeric type" do
+      let(:attribs) { { type: "numeric", answer_options: nil } }
+      it "renders the guidance partial for numeric questions" do
+        expect(rendered).to match(expected_guidance)
+      end
+    end
+
+    context "with select type" do
+      let(:attribs) { { type: "select", answer_options: {"1": "A", "2": "B"} } }
+      it "renders the guidance partial for select questions" do
+        expect(rendered).to match(expected_guidance)
+      end
+    end
+
+    context "with checkbox type" do
+      let(:attribs) { { type: "checkbox", answer_options: {"1": "A", "2": "B"} } }
+      it "renders the guidance partial for checkbox questions" do
+        expect(rendered).to match(expected_guidance)
+      end
+    end
+
+    context "with date type" do
+      let(:attribs) { { type: "date", answer_options: nil } }
+      it "renders the guidance partial for date questions" do
+        expect(rendered).to match(expected_guidance)
+      end
+    end
+  end
+end