Unit Testing Email Content

Question

I'm usually one to say any piece of code no matter what it does, especially if it's runs in a production environment should be tested. I've been wondering, however, if dynamic email content should be an exception. It changes so often and is usually a pain to properly and fully test that I don't know if it's worth it. More often than not, the content of the unit test is copy/pasted anyway (I know this is not ideal, but happens nonetheless), so it's not really giving any real benefit other than telling us if something will severely blow up, and a simple unit test just trying to send the email (not verifying the copy) should take care of that.

I was hoping to get some opinions from other developers. Let me know what you think. Unit test email content or not?

Edit: Just to clarify, we already have separate unit/integration tests for the actual sending of emails, this question is referring to just testing the content of an email. Currently we unit test only the dynamic content, the template text is not aside from click testing.

Answer 1

You should always test everything, yes, but you can't always unit test everything. In this case, trying to verify that an email template has been produced correctly is probably better off in integration and user acceptance testing.

You can unit test how your programs build email templates, however, and this is the route I recommend you go.

Build an API for filling an email template, a helper class with methods like:

// using C# syntax returning strings for the example -- you could just as easily return
// System.Net.Mail.MailMessage or javax.mail.Message instead
string BuildPasswordChangeTemplate(string username, string newPassword, string email);
string BuildErrorTeplate(string methodName, string serviceName, Exception e);

As long as the methods are defined in an interface or virtual (and aren't static), you can mock the helper class and unit test that your code calls into the appropriate template builder at the appropriate time. You can then push spelling and format and those other things to user acceptance testing and consider your work done.