Purolator does not have a test account number you can use, but you can switch on demo mode after creating a Purolator Preference
Follow the instructions below to do this:
1. Navigate to Setup | Develop | Custom Settings
2. Click Shipmate General Settings
3. Click Manage
4. Click New
5. Provide a Name and check Run Demo Mode
Once that's been done you can start testing the Purolator app and you won't be charged for any of these test shipments.