Prerequisites:

1. A Moodle installation that is visible on the internet.
2. A PayPal developer account and sandbox accounts (at least 1 facilitator/business and 1 buyer account). For more information, see https://developer.paypal.com/developer/accounts/
3. Optional: Set up Moodle SMTP settings.
4. Set $CFG->usepaypalsandbox = true; in your config.php to use sandbox account for testing.

Test

1. Log in as an administrator and enable PayPal enrolment via 'Manage enrol plugins' in the Site administration.
2. In the PayPal enrolment settings, set "Paypal business email" to PayPal facilitator sandbox account.
3. Go to a course (c1) and go to 'Enrolment methods' via the gear menu or the Administration block (depending upon your theme).
4. Add PayPal as an enrolment method and set "Enrol cost" to 1
5. Log in as a student and attempt to enrol in the course by clicking the "Send payment via PayPal" button
6. Confirm payment and click on the link to go back to your Moodle site.
7. Verify that you are enrolled in the course
8. Log in as an administrator again and backup the course
9. Restore it as a new course and verify that it has PayPal as an enrolment method.