How design patterns can help you in developing unit testing-enabled applications

using Castle.ActiveRecord;
using NHibernate;
using Northwind.DataAccess;
using Northwind.DataAccess.Repository;
using Northwind.Domain.Model;
using NUnit.Framework;
using System;
using System.Collections.Generic;
using System.Text;

namespace Northwind.DataAccess.Test
{
    [TestFixture]
    public class InMemoryCustomerRepositoryTest
    {
        private Customer customer;
        private InMemoryCustomerRepository customerRepository;

        [SetUp]
        public void Setup()
        {
            customer = new Customer();
            customerRepository = new InMemoryCustomerRepository();
            //We must initialize ActiveRecord db settings before working with ActiveRecords.
            DataAccessHelper.Initialize();
        }

        [Test]
        public void InsertAndGetCustomerTest()
        {
            Customer c = new Customer();
            Assert.AreEqual(true, c.IsNew, "c.IsNew");
            c.ID = "TEST";
            c.CompanyName = "CUSTOMER TEST";
            c.ContactName = "CONTACT TEST";
            using (ISession session = DataAccessHelper.SessionFactory.OpenSession())
            {
                session.BeginTransaction();
                customerRepository.AddOrUpdate(session, c);
                session.Transaction.Commit();
            }
            Assert.AreEqual(false, c.IsNew, "c.IsNew");
            Customer c2 = customerRepository.Load("TEST");
            using (ISession session = DataAccessHelper.SessionFactory.OpenSession())
            {
                session.BeginTransaction();
                customerRepository.Remove(session, c2);
                session.Transaction.Commit();
            }
        }

        [Test]
        public void InsertAndUpdateCustomerTest()
        {
            Customer c = new Customer();
            c.ID = "TEST";
            c.CompanyName = "CUSTOMER TEST";
            c.ContactName = "CONTACT TEST";
            using (ISession session = DataAccessHelper.SessionFactory.OpenSession())
            {
                session.BeginTransaction();
                customerRepository.AddOrUpdate(session, c);
                session.Transaction.Commit();
            }
            Customer c2 = customerRepository.Load("TEST");
            c2.CompanyName = "CUSTOMER TEST UPDATED";
            c2.ContactName = "CONTACT TEST UPDATED";
            using (ISession session = DataAccessHelper.SessionFactory.OpenSession())
            {
                session.BeginTransaction();
                customerRepository.AddOrUpdate(session, c2);
                session.Transaction.Commit();
            }
            Customer c3 = customerRepository.Load("TEST");
            Assert.AreEqual("CUSTOMER TEST UPDATED", c3.CompanyName);
            Customer c4 = customerRepository.Load("TEST");
            using (ISession session = DataAccessHelper.SessionFactory.OpenSession())
            {
                session.BeginTransaction();
                customerRepository.Remove(session, c4);
                session.Transaction.Commit();
            }
        }

        [Test]
        public void InsertAndDeleteCustomerTest()
        {
            Customer c = new Customer();
            c.ID = "TEST";
            c.CompanyName = "CUSTOMER TEST";
            c.ContactName = "CONTACT TEST";
            using (ISession session = DataAccessHelper.SessionFactory.OpenSession())
            {
                session.BeginTransaction();
                customerRepository.AddOrUpdate(session, c);
                session.Transaction.Commit();
            }
            Customer c2 = customerRepository.Load("TEST");
            using (ISession session = DataAccessHelper.SessionFactory.OpenSession())
            {
                session.BeginTransaction();
                customerRepository.Remove(session, c2);
                session.Transaction.Commit();
            }
            try
            {
                Customer c3 = customerRepository.Load("TEST");
                Assert.IsTrue(c3 == null, "customer has not been deleted");
            }
            catch
            {
            }
        }

        [TearDown]
        public void TearDown()
        {
        }
    }
}