If you are new to Force.com Email Services and having a hard time writing test methods for your Apex code, this code sample might help you get started.
You can receive email attachments with inbound emails and often you want to build Apex code that uses the attachments. How do I create an inline attachments for the test method?
The example below shows you how you can create a new email message and assign the attachments to it. You can also find the code sample here.