Sending mails using the .NET’s SmtpClient API is very easy and straightforward. Alas the same doesn’t count for mocking the client in your unit test. So most of the time I create an extra layer of abstraction and wrap the SmtpClient in an IEmailService. And this works fine for my unit tests.
But for my integration tests I follow a different strategy. By default, the SmtpClient takes mail server settings from your web.config or app.config file.
To configure it to send e-mail through a particular SMTP server, add the following to your web.config file:
4: <smtp deliveryMethod="Network">
5: <network host="smtp.example.com"/>
But this means that an actual mail server has to be configured to run my integration tests and even worse that some test mails will be send out to everyone.
Instead it would be better if you could write mails to a local directory, so you can see what’s happening without having to set up an actual mail server. This is done very easily, change your config to use these settings:
4: <smtp deliveryMethod="SpecifiedPickupDirectory">
5: <specifiedPickupDirectory pickupDirectoryLocation="c:\emails" />
This will write .eml files to the specified folder, which must already exist and be writable. If you double-click .eml files in Windows Explorer, they’ll open in Outlook Express or Windows Mail.