fixed issue occurring for progress bars without a value

app/helpers/application_helper.rb

@@ -33,8 +33,8 @@ module ApplicationHelper
   end
 
   def progress_bar(value)
-    content_tag(:div, class: 'progress') do
+    content_tag(:div, class: value ? 'progress' : 'disabled progress') do
-      content_tag(:div, "#{value}%", :'aria-valuemax' => 100, :'aria-valuemin' => 0, :'aria-valuenow' => value, class: 'progress-bar progress-bar-striped', role: 'progressbar', style: "width: #{[value, 100].min}%;")
+      content_tag(:div, value ? "#{value}%" : '', :'aria-valuemax' => 100, :'aria-valuemin' => 0, :'aria-valuenow' => value, class: 'progress-bar progress-bar-striped', role: 'progressbar', style: "width: #{[value || 0, 100].min}%;")
     end
   end
 

spec/controllers/exercises_controller_spec.rb

@@ -182,6 +182,14 @@ describe ExercisesController do
     expect_template(:show)
   end
 
+  describe 'GET #statistics' do
+    before(:each) { get :statistics, id: exercise.id }
+
+    expect_assigns(exercise: :exercise)
+    expect_status(200)
+    expect_template(:statistics)
+  end
+
   describe 'POST #submit' do
     let(:output) { {} }
     let(:request) { post :submit, format: :json, id: exercise.id, submission: {cause: 'submit', exercise_id: exercise.id} }

spec/helpers/application_helper_spec.rb

@@ -43,6 +43,8 @@ describe ApplicationHelper do
 
   describe '#progress_bar' do
     let(:html) { progress_bar(value) }
+
+    context 'with a value' do
       let(:value) { 42 }
 
       it "builds nested 'div' tags" do
@@ -58,6 +60,23 @@ describe ApplicationHelper do
       end
     end
 
+    context 'without a value' do
+      let(:value) { nil }
+
+      it 'does not raise an error' do
+        expect { html }.not_to raise_error
+      end
+
+      it 'assigns the correct classes' do
+        expect(html).to have_css('div.disabled.progress div.progress-bar')
+      end
+
+      it 'uses the correct width' do
+        expect(html).to have_css("div.progress-bar[style='width: 0%;']")
+      end
+    end
+  end
+
   describe '#row' do
     let(:html) { row(label: 'foo', value: 42) }