Add coverage report badge metadata class

config/routes.rb

@@ -869,7 +869,10 @@ Rails.application.routes.draw do
         resources :badges, only: [:index] do
           collection do
             scope '*ref', constraints: { ref: Gitlab::Regex.git_reference_regex } do
-              get :build, constraints: { format: /svg/ }
+              constraints format: /svg/ do
+                get :build
+                get :coverage
+              end
             end
           end
         end

lib/gitlab/badge/coverage/metadata.rb

+module Gitlab
+  module Badge
+    module Coverage
+      ##
+      # Class that describes coverage badge metadata
+      #
+      class Metadata
+        include Gitlab::Application.routes.url_helpers
+        include ActionView::Helpers::AssetTagHelper
+        include ActionView::Helpers::UrlHelper
+
+        def initialize(badge)
+          @project = badge.project
+          @ref = badge.ref
+          @job = badge.job
+        end
+
+        def to_html
+          link_to(image_tag(image_url, alt: 'coverage report'), link_url)
+        end
+
+        def to_markdown
+          "[![coverage report](#{image_url})](#{link_url})"
+        end
+
+        def image_url
+          coverage_namespace_project_badges_url(@project.namespace,
+                                                @project, @ref,
+                                                format: :svg)
+        end
+
+        def link_url
+          namespace_project_commits_url(@project.namespace, @project, id: @ref)
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/badge/coverage/metadata_spec.rb

+require 'spec_helper'
+require 'lib/gitlab/badge/shared/metadata'
+
+describe Gitlab::Badge::Coverage::Metadata do
+  let(:badge) do
+    double(project: create(:project), ref: 'feature', job: 'test')
+  end
+
+  let(:metadata) { described_class.new(badge) }
+
+  it_behaves_like 'badge metadata'
+
+  describe '#image_url' do
+    it 'returns valid url' do
+      expect(metadata.image_url).to include 'badges/feature/coverage.svg'
+    end
+  end
+
+  describe '#link_url' do
+    it 'returns valid link' do
+      expect(metadata.link_url).to include 'commits/feature'
+    end
+  end
+end