Merge branch 'service-tests' into 'master'

Add tests for (Create|Update)ReleaseService

As promised 

See merge request !1875

spec/services/create_release_service_spec.rb

+require 'spec_helper'
+
+describe CreateReleaseService do
+  let(:project) { create(:project) }
+  let(:user) { create(:user) }
+  let(:tag_name) { project.repository.tag_names.first }
+  let(:description) { 'Awesome release!' }
+  let(:service) { CreateReleaseService.new(project, user) }
+
+  it 'creates a new release' do
+    result = service.execute(tag_name, description)
+    expect(result[:status]).to eq(:success)
+    release = project.releases.find_by(tag: tag_name)
+    expect(release).not_to be_nil
+    expect(release.description).to eq(description)
+  end
+
+  it 'raises an error if the tag does not exist' do
+    result = service.execute("foobar", description)
+    expect(result[:status]).to eq(:error)
+  end
+
+  context 'there already exists a release on a tag' do
+    before do
+      service.execute(tag_name, description)
+    end
+
+    it 'raises an error and does not update the release' do
+      result = service.execute(tag_name, 'The best release!')
+      expect(result[:status]).to eq(:error)
+      expect(project.releases.find_by(tag: tag_name).description).to eq(description)
+    end
+  end
+end

spec/services/update_release_service_spec.rb

+require 'spec_helper'
+
+describe UpdateReleaseService do
+  let(:project) { create(:project) }
+  let(:user) { create(:user) }
+  let(:tag_name) { project.repository.tag_names.first }
+  let(:description) { 'Awesome release!' }
+  let(:new_description) { 'The best release!' }
+  let(:service) { UpdateReleaseService.new(project, user) }
+
+  context 'with an existing release' do
+    let(:create_service) { CreateReleaseService.new(project, user) }
+
+    before do
+      create_service.execute(tag_name, description)
+    end
+
+    it 'successfully updates an existing release' do
+      result = service.execute(tag_name, new_description)
+      expect(result[:status]).to eq(:success)
+      expect(project.releases.find_by(tag: tag_name).description).to eq(new_description)
+    end
+  end
+
+  it 'raises an error if the tag does not exist' do
+    result = service.execute("foobar", description)
+    expect(result[:status]).to eq(:error)
+  end
+
+  it 'raises an error if the release does not exist' do
+    result = service.execute(tag_name, description)
+    expect(result[:status]).to eq(:error)
+  end
+end