mocking-tests.cs

using Microsoft.VisualStudio.TestTools.UnitTesting;
using Moq;

[TestClass]
public class MockingTests
{
    [TestMethod]
    public void should_send_an_email()
    {
        var mockEmailService = new Mock<IEmailService>();

        GreetingBuilder3 sut = new GreetingBuilder3(mockEmailService.Object);

        sut.Build("[email protected]", "joe");

        mockEmailService.Verify(es => es.Send("[email protected]", "hello, joe!"));
    }
}