Pull out this one to a helper

app/helpers/application_helper.rb

@@ -53,4 +53,8 @@ def insulin_for_time
     end
     'humalog'
   end
+
+  def class_for_table_cell metric, field
+    "#{metric.class.name.underscore.gsub('_', '-')}-#{field}"
+  end
 end

app/views/welcome/index.html.erb

@@ -26,7 +26,7 @@
         </td>
         <% count = 0 %>
         <% class_name(value).fields.each do |field| %>
-          <td class='<%= "#{value.class.name.underscore.gsub('_', '-')}-#{field}" %>'>
+          <td class='<%= class_for_table_cell value, field %>'>
             <% if value.class.units[:applies_to] == field.to_sym %>
               <span class='value' data-toggle='tooltip' data-placement='top' title='<%= value.send(field) %> <%= value.class.units[:full] %>'>
                 <%= value.send(field) %> <%= value.class.units[:short] %>

spec/helpers/application_helper_spec.rb

@@ -29,21 +29,28 @@
 
   describe '#insulin_for_time' do
     it 'defaults to humalog' do
-      Timecop.freeze 2016, 02, 16, 12, 00
-      expect(helper.insulin_for_time).to eq 'humalog'
-      Timecop.return
+      Timecop.freeze 2016, 02, 16, 12, 00 do
+        expect(helper.insulin_for_time).to eq 'humalog'
+      end
     end
-    
+
     it 'knows lantus is for bedtime' do
-      Timecop.freeze 2016, 02, 16, 22, 00
+      Timecop.freeze 2016, 02, 16, 22, 00 do
         expect(helper.insulin_for_time).to eq 'lantus'
-      Timecop.return
+      end
     end
 
     it 'thinks bedtime lasts until 06:00' do
-      Timecop.freeze 2016, 02, 16, 06, 00
-      expect(helper.insulin_for_time).to eq 'lantus'
-      Timecop.return
+      Timecop.freeze 2016, 02, 16, 06, 00 do
+        expect(helper.insulin_for_time).to eq 'lantus'
+      end
+    end
+  end
+
+  describe '#class_for_table_cell' do
+    let(:metric) { build :medication_event }
+    it 'generates the correct class' do
+      expect(helper.class_for_table_cell metric, 'insulin').to eq 'medication-event-insulin'
     end
   end
 end