Hi,

I'm getting started with unit testing and trying to do some TDD. I've read a fair bit about the subject and written a few tests. I just want to know if the following is the right approach.

I want to add the usual "contact us" facility on my web site. You know the thing, the user fills out a form with their email address, enters a brief message and hits a button to post the form back.

The model binders do their stuff and my action method accepts the posted data as a model. The action method would then parse the model and use smtp to send an email to the web site administrator infoming him/her that somebody filled out the contact form on their site.

Now for the question .... In order to test this, would I be right in creating an interface IDeliver that has a method Send(emailAddress, message) to accept the email address and message body. Implement the inteface in a concrete class and let that class deal with smtp stuff and actually send the mail.

If I add the inteface as a parameter to my controller constructor I can then use DI and IoC to inject the concrete class into the controller. But when unit testing I can create a fake or mock version of my IDeliver and do assertions on that.

The reason I ask is that I've seen other examples of people generating interfaces for SmtpClient and then mocking that. Is there really any need to go that far or am I not understanding this stuff?