Add test for the burndown chart feature

qa/qa/specs/features/ee/browser_ui/2_plan/burndown_chart/burndown_chart_spec.rb

+# frozen_string_literal: true
+
+module QA
+  context 'Plan' do
+    describe 'Burndown chart' do
+      include ::QA::Support::Dates
+
+      let(:project) do
+        Resource::Project.fabricate_via_api! do |project|
+          project.name = 'project-to-test-burndown-chart'
+        end
+      end
+
+      let(:milestone) do
+        QA::EE::Resource::ProjectMilestone.fabricate_via_api! do |m|
+          m.project = project
+          m.title = 'v1'
+          m.start_date = current_date_yyyy_mm_dd
+          m.due_date = next_month_yyyy_mm_dd
+        end
+      end
+
+      before do
+        Runtime::Browser.visit(:gitlab, Page::Main::Login)
+        Page::Main::Login.perform(&:sign_in_using_credentials)
+
+        weight_of_two = 2
+
+        create_issue('Issue 1', project, milestone, weight_of_two)
+        create_issue('Issue 2', project, milestone, weight_of_two)
+      end
+
+      it 'shows burndown chart on milestone page' do
+        milestone.visit!
+
+        Page::Project::Milestone::Show.perform do |show|
+          expect(show.burndown_chart).to be_visible
+          expect(show.burndown_chart).to have_content("Open issues")
+
+          show.click_weight_button
+
+          expect(show.burndown_chart).to have_content('Open issue weight')
+        end
+      end
+
+      def create_issue(title, project, milestone, weight)
+        Resource::Issue.fabricate_via_api! do |issue|
+          issue.project = project
+          issue.title = title
+          issue.milestone = milestone
+          issue.weight = weight
+        end
+      end
+    end
+  end
+end