1. Create course
2. Add External tool, next to "Preconfigured tool" click "+" and fill the form, complete creating of external tool
3. Add another external tool, make sure you can select this preconfigured tool and it is located under "Course tools" heading
4. Check in the DB that you have entries in lti_types table pointing to this course
5. Delete the course
6. Check in the DB that you no longer have entries in lti_types table pointing to this course

Last step currently fails.

Another scenario:

1. Repeat steps 1-4 above
2. Restore another course backup into this course choosing to delete current course contents
3. Add a new external tool and make sure there is nothing in preconfigured "Course tool" from before the restore

P.S. course reset is also not implemented for External tools