Add group service spec.

spec/services/milestones/group_service_spec.rb

+require 'spec_helper'
+
+describe Milestones::GroupService do
+  let(:user) { create(:user) }
+  let(:user2) { create(:user) }
+  let(:group) { create(:group) }
+  let(:project1) { create(:project, group: group) }
+  let(:project2) { create(:project, path: 'gitlab-ci', group: group) }
+  let(:project3) { create(:project, path: 'cookbook-gitlab', group: group) }
+  let(:milestone1_project1) { create(:milestone, title: "Milestone v1.2", project: project1) }
+  let(:milestone1_project2) { create(:milestone, title: "Milestone v1.2", project: project2) }
+  let(:milestone1_project3) { create(:milestone, title: "Milestone v1.2", project: project3) }
+  let(:milestone2_project1) { create(:milestone, title: "VD-123", project: project1) }
+  let(:milestone2_project2) { create(:milestone, title: "VD-123", project: project2) }
+  let(:milestone2_project3) { create(:milestone, title: "VD-123", project: project3) }
+
+  describe 'execute' do
+    context 'with valid projects' do
+      before do
+        milestones =
+          [ 
+            milestone1_project1,
+            milestone1_project2,
+            milestone1_project3,
+            milestone2_project1,
+            milestone2_project2,
+            milestone2_project3
+          ]
+        @group_milestones = Milestones::GroupService.new(milestones).execute
+      end
+
+      it 'should have all project milestones' do
+        expect(@group_milestones.count).to eq(2)
+      end
+
+      it 'should have all project milestones titles' do
+        expect(@group_milestones.map { |group_milestone| group_milestone.title }).to match_array(['Milestone v1.2', 'VD-123'])
+      end
+
+      it 'should have all project milestones' do
+        expect(@group_milestones.map { |group_milestone| group_milestone.milestones.count }.sum).to eq(6)
+      end
+    end
+  end
+
+  describe 'milestone' do
+    context 'with valid title' do
+      before do
+        milestones =
+          [ 
+            milestone1_project1,
+            milestone1_project2,
+            milestone1_project3,
+            milestone2_project1,
+            milestone2_project2,
+            milestone2_project3
+          ]
+        @group_milestones = Milestones::GroupService.new(milestones).milestone('Milestone v1.2')
+      end
+
+      it 'should have exactly one group milestone' do
+        expect(@group_milestones.title).to eq('Milestone v1.2')
+      end
+
+      it 'should have all project milestones with the same title' do
+        expect(@group_milestones.milestones.count).to eq(3)
+      end
+    end
+  end
+end