Modifies the overview page so when there is an empty dataset, there is clearer explanatory text and an empty version of the variance chart. Finishes #180118088

app/helpers/variance_helper.rb

@@ -16,6 +16,7 @@ module VarianceHelper
   end
 
   def graph_background_height(number_of_rows:)
+    number_of_rows += 1 if @has_empty_dataset
     graph_height(number_of_rows) - footer_gutter
   end
 

app/views/overview/_variance_chart.html.erb

@@ -1,7 +1,9 @@
 <% displayed_presenters = presenters.filter { |p| p.sufficient_data? }.sort %>
 <% not_displayed_presenters = presenters - displayed_presenters %>
 
-<% if not_displayed_presenters.present? %>
+<% if displayed_presenters.none? %>
+  <p class="caption mb-5">Note: No measures can be displayed due to limited availability of school admin data and/or low survey response rates.</p>
+<% elsif not_displayed_presenters.present? %>
   <p class="caption mb-5">Note: The following measures are not displayed due to limited availability of school admin data and/or low survey response rates: <%= not_displayed_presenters.map(&:measure_name).join('; ') %>.</p>
 <% end %>
 
@@ -87,6 +89,18 @@
           <%= presenter.measure_name %>
         </text>
       <% end %>
+
+      <% if displayed_presenters.none? %>
+        <text
+          class="font-cabin"
+          x="0"
+          y="<%= 0 * measure_row_height + measure_row_height / 2 %>"
+          dominant-baseline="middle"
+          data-variance-row-label
+        >
+        Insufficient data
+        </text>
+      <% end %>
     </svg>
 
     <svg

spec/views/dashboard/variance_chart.html.erb_spec.rb

@@ -1,6 +1,7 @@
 require 'rails_helper'
 
 describe 'overview/_variance_chart.html.erb' do
+  context 'When there are scores to show' do
     subject { Nokogiri::HTML(rendered) }
 
     let(:higher_scoring_measure) { create(:measure) }
@@ -16,11 +17,37 @@ describe 'overview/_variance_chart.html.erb' do
     end
 
     it 'displays higher scoring measures above lower scoring measures' do
-    measure_row_bars = subject.css("rect.measure-row-bar")
+      measure_row_bars = subject.css('rect.measure-row-bar')
 
-    higher_scoring_measure_index = measure_row_bars.find_index { |bar| bar['data-for-measure-id'] == higher_scoring_measure.measure_id }
-    lower_scoring_measure_index = measure_row_bars.find_index { |bar| bar['data-for-measure-id'] == lower_scoring_measure.measure_id }
+      higher_scoring_measure_index = measure_row_bars.find_index do |bar|
+        bar['data-for-measure-id'] == higher_scoring_measure.measure_id
+      end
+      lower_scoring_measure_index = measure_row_bars.find_index do |bar|
+        bar['data-for-measure-id'] == lower_scoring_measure.measure_id
+      end
 
       expect(higher_scoring_measure_index).to be < lower_scoring_measure_index
     end
   end
+
+  context 'When there are no scores to show for any measures' do
+    before :each do
+      measure_lacking_score = create(:measure)
+      another_measure_lacking_score = create(:measure)
+      presenters = [
+        VarianceChartRowPresenter.new(measure: measure_lacking_score, score: Score.new(nil)),
+        VarianceChartRowPresenter.new(measure: another_measure_lacking_score, score: Score.new(nil))
+      ]
+
+      render partial: 'variance_chart', locals: { presenters: presenters}
+    end
+
+    it "displays the text 'insufficient data' for an empty dataset" do
+      expect(rendered).to have_text 'Insufficient data'
+    end
+
+    it "does not display the partial data text: 'The following measures are not displayed due to limited availability of school admin data and/or low survey response rates:' " do
+      expect(rendered).not_to have_text 'The following measures are not displayed due to limited availability of school admin data and/or low survey response rates:'
+    end
+  end
+end