Memoize node presenters

app/presenters/flow_presenter.rb

@@ -14,6 +14,7 @@ def initialize(request, flow)
     @request = request
     @params = request.params
     @flow = flow
+    @node_presenters = {}
   end
 
   def artefact
@@ -74,9 +75,10 @@ def presenter_for(node)
                         QuestionPresenter
                       when SmartAnswer::Outcome
                         OutcomePresenter
-                      else NodePresenter
+                      else
+                        NodePresenter
                       end
-    presenter_class.new(node, current_state)
+    @node_presenters[node.name] ||= presenter_class.new(node, current_state)
   end
 
   def current_question_number
@@ -93,7 +95,7 @@ def current_node
 
   def start_node
     node = SmartAnswer::Node.new(@flow, @flow.name.underscore.to_sym)
-    StartNodePresenter.new(node)
+    @start_node ||= StartNodePresenter.new(node)
   end
 
   def change_collapsed_question_link(question_number)

test/unit/flow_presenter_test.rb

@@ -0,0 +1,90 @@
+require_relative "../test_helper"
+
+class FlowPresenterTest < ActiveSupport::TestCase
+  setup do
+    @flow = SmartAnswer::Flow.new do
+      name 'flow-name'
+      value_question :first_question_key
+    end
+    @request = ActionDispatch::TestRequest.new
+    @flow_presenter = FlowPresenter.new(@request, @flow)
+  end
+
+  test '#presenter_for returns presenter for Date question' do
+    question = @flow.date_question(:question_key).last
+    node_presenter = @flow_presenter.presenter_for(question)
+    assert_instance_of DateQuestionPresenter, node_presenter
+  end
+
+  test '#presenter_for returns presenter for CountrySelect question' do
+    question = @flow.country_select(:question_key).last
+    node_presenter = @flow_presenter.presenter_for(question)
+    assert_instance_of CountrySelectQuestionPresenter, node_presenter
+  end
+
+  test '#presenter_for returns presenter for MultipleChoice question' do
+    question = @flow.multiple_choice(:question_key).last
+    node_presenter = @flow_presenter.presenter_for(question)
+    assert_instance_of MultipleChoiceQuestionPresenter, node_presenter
+  end
+
+  test '#presenter_for returns presenter for Checkbox question' do
+    question = @flow.checkbox_question(:question_key).last
+    node_presenter = @flow_presenter.presenter_for(question)
+    assert_instance_of CheckboxQuestionPresenter, node_presenter
+  end
+
+  test '#presenter_for returns presenter for Value question' do
+    question = @flow.value_question(:question_key).last
+    node_presenter = @flow_presenter.presenter_for(question)
+    assert_instance_of ValueQuestionPresenter, node_presenter
+  end
+
+  test '#presenter_for returns presenter for Money question' do
+    question = @flow.money_question(:question_key).last
+    node_presenter = @flow_presenter.presenter_for(question)
+    assert_instance_of MoneyQuestionPresenter, node_presenter
+  end
+
+  test '#presenter_for returns presenter for Salary question' do
+    question = @flow.salary_question(:question_key).last
+    node_presenter = @flow_presenter.presenter_for(question)
+    assert_instance_of SalaryQuestionPresenter, node_presenter
+  end
+
+  test '#presenter_for returns presenter for other question types' do
+    question = @flow.send(:add_question, SmartAnswer::Question::Base, :question_key).last
+    node_presenter = @flow_presenter.presenter_for(question)
+    assert_instance_of QuestionPresenter, node_presenter
+  end
+
+  test '#presenter_for returns presenter for outcome' do
+    outcome = @flow.outcome(:outcome_key).last
+    node_presenter = @flow_presenter.presenter_for(outcome)
+    assert_instance_of OutcomePresenter, node_presenter
+  end
+
+  test '#presenter_for returns presenter for other node types' do
+    node = @flow.send(:add_question, SmartAnswer::Node, :node_key).last
+    node_presenter = @flow_presenter.presenter_for(node)
+    assert_instance_of NodePresenter, node_presenter
+  end
+
+  test '#presenter_for always returns same presenter for a given question' do
+    question = @flow.multiple_choice(:question_key).last
+    node_presenter_1 = @flow_presenter.presenter_for(question)
+    node_presenter_2 = @flow_presenter.presenter_for(question)
+    assert_same node_presenter_1, node_presenter_2
+  end
+
+  test '#start_node returns presenter for landing page node' do
+    start_node = @flow_presenter.start_node
+    assert_instance_of StartNodePresenter, start_node
+  end
+
+  test '#start_node always returns same presenter for landing page node' do
+    start_node_1 = @flow_presenter.start_node
+    start_node_2 = @flow_presenter.start_node
+    assert_same start_node_1, start_node_2
+  end
+end