update

spec/models/registration_spec.rb

@@ -0,0 +1,25 @@
+#!/bin/env ruby
+# encoding: utf-8
+require 'spec_helper'
+
+describe 'Registration' do
+  describe 'validations' do
+    it 'has a valid factory' do
+      expect(build(:registration)).to be_valid
+    end
+
+    describe 'registration_limit_not_exceed' do
+      it 'is not valid when limit exceeded' do
+        conference = build(:conference)
+        conference.registration_limit = 1
+        registration1 = build(:registration, conference: conference)
+        registration1.save
+        registration2 = build(:registration, conference: conference)
+        registration2.save
+        expect(conference.registrations.size).to be 1
+        expect(registration2.valid?).to be false
+        expect(registration2.errors.full_messages).to eq(['Registration limit exceeded'])
+      end
+    end
+  end
+end