1. Create a new unit test project under your existing solution called Packt.Xrm.UnitTest.
2. Add a reference to the Moq NuGet package as well as Microsoft.CrmSdk.CoreAssemblies.
3. Add a reference to your existing Packt.Xrm.Extensions (refactored) project.
4. Create a new Basic Unit Test class called EmailUpdateBusinessLogicTest.

5. Add the following using statements:

using Packt.Xrm.Extensions.BusinessLogic; 
using Packt.Xrm.Extensions.DataAccessLayer; 
using Moq; 
using Packt.Xrm.Entities; 
using Microsoft.Xrm.Sdk; 
using System.Collections.Generic; 

6. Add the following private instance variables:

private Mock<IEmailDataAccessLayer> _emailDalMock; 
private Mock<ICustomTracingService> _tracing; 

7. Create a private SetupMocks method with the following implementation:

private void SetupMocks() 
{ 
  _emailDalMock = new Mock<IEmailDataAccessLayer>(); 
  _emailDalMock.Setup(dal => dal.GetEmails(It.IsAny<Guid>
    ())).Returns( 
       new List<Email>() { new Email() { Subject = "sample1"},
       new Email { Subject = "sample2" }, 
       new Email { Subject = string.Empty }  } 
        ); 
    _tracing = new Mock<ICustomTracingService>(); 
} 

8. Create a TestUpdateEmail test method with the following implementation:

[TestMethod] 
public void TestUpdateEmail() 
{ 
    //Arrange 
    SetupMocks(); 

    var businessLogic = new UpdateEmailLogic(_emailDalMock.Object, _tracing.Object); 

    //Act 
    businessLogic.UpdateAccountsEmails(Guid.NewGuid()); 

    //Assert  
    _emailDalMock.Verify(dal => dal.CloseEmailAsCancelled(It.IsAny<Email>()), Times.Exactly(1)); 
    _emailDalMock.Verify(dal => dal.UpdateEntity(It.IsAny<Entity>()), Times.Exactly(2)); 
    _tracing.Verify(trace => trace.Trace("{0} closed emails and {1} updated emails", 1, 2), Times.Exactly(1)); 
}