Add spec for milestone total weight on the milestone summary

spec/features/projects/milestones/milestone_spec.rb

+require 'spec_helper'
+
+describe 'Milestones', feature: true do
+  context 'milestone summary' do
+    let(:project) { create(:empty_project, :public) }
+    let(:milestone) { create(:milestone, project: project) }
+
+    it 'shows the total weight when sum is greater than zero' do
+      create(:issue, project: project, milestone: milestone, weight: 3)
+      create(:issue, project: project,  milestone: milestone, weight: 1)
+
+      visit_milestone_page
+
+      within '.milestone-summary' do
+        expect(page).to have_content 'Total weight: 4'
+      end
+    end
+
+    it 'hides the total weight when sum is equal to zero' do
+      create(:issue, project: project, milestone: milestone, weight: nil)
+      create(:issue, project: project,  milestone: milestone, weight: nil)
+
+      visit_milestone_page
+
+      within '.milestone-summary' do
+        expect(page).not_to have_content 'Total weight:'
+      end
+    end
+
+    def visit_milestone_page
+      visit namespace_project_milestone_path(project.namespace.to_param, project.to_param, milestone.to_param)
+    end
+  end
+end