How to mock non virtual methods?

Question

[TestMethod]
public void TestMethod1()
{
    var mock = new Mock<EmailService>();
    mock.Setup(x => x.SendEmail()).Returns(true);
    var cus = new Customer();
    var result = cus.AddCustomer(mock.Object);
    Assert.IsTrue(result);
}

public class Customer
{
    public bool AddCustomer(EmailService emailService)
    {
        emailService.SendEmail();
        Debug.WriteLine("new customer added");
        return true;
    }
}

public class EmailService
{            
    public virtual bool SendEmail()
    {
        throw  new Exception("send email failed cuz bla bla bla");
    }
}

The EmailService.SendEmail method must be virtual to mock it. Is there any way to mock non virtual methods?

Answer 1

Moq cannot mock non virtual methods on classes. Either use other mocking frameworks such as Type mock Isolator which actually weaves IL into your assembly or place an interface on EmailService and mock that.

Answer 2

Mocking non virtual methods involves the use of low level profiler API. At the moment I think the only options available are :

• TypeMock
• JustMock

both are commercial, even if JustMock have a lite edition, mocking non virtual methods are available just with the commercial version. As pointed in the comments there is something from Microsoft research, in the project Pex and Moles

Answer 3

Updated july 2020: pose Has been abandoned, current recommendation is: https://github.com/riezebosch/Unmockable Thanks to @Customizer for pointing out.

I was also checking out https://github.com/Serg046/AutoFake which seems viable from @Serg046 —— Use pose. Allows you to replace any method including static or non virtual. Fairly new project, but fully open source MIT license. https://github.com/tonerdo/pose