There are two ways to delete test Contact records:
Manually go to each Contact record, click the Manage External User button and select Disable Customer User. Once you have disabled the user you can now click Delete and delete the contact.

Using either Data Loader or Informatica, update the Test User Records you want to disable by mapping FALSE to the field IsPortalEnabled. This will disable the Community User.
Important: ensure you have filtered and are only updating Test Records or Records you wish to delete. If you disable an active User, the Student will need to recreate their user account to sign back into the system.
Set the following details when creating an Informatica task to update the Test User Records you want to delete:
Set the Task Definition:
Specify the Source:
Define the Target:
Set the Data Filters:
Define the Field Mapping:
Schedule and Run the task.
Important: be sure to TEST that your filter criteria is correct. You can set the Target to your dropbox and create a file to validate that the correct records are being selected. You will want to add additional fields to the mapping in order to validate the users included in the filter.
Export the User object.
You can either create a filter here OR export ALL records and manually remove the unwanted records from the file.
Select the following Fields: