Add minimial test coverage for delete branch service

spec/services/delete_branch_service_spec.rb

+require 'spec_helper'
+
+describe DeleteBranchService, services: true do
+  let(:project) { create(:project) }
+  let(:user) { create(:user) }
+  let(:service) { described_class.new(project, user) }
+
+  describe '#execute' do
+    let(:result) { service.execute('feature') }
+
+    context 'when user has access to push to repository' do
+      before do
+        project.team << [user, :developer]
+      end
+
+      it 'removes the branch' do
+        expect(result[:status]).to eq :success
+      end
+    end
+
+    context 'when user does not have access to push to repository' do
+      it 'does not remove branch' do
+        expect(result[:status]).to eq :error
+        expect(result[:message]).to eq 'You dont have push access to repo'
+      end
+    end
+  end
+end