All tests are chargeable, with distinct rates for members and non-members.
Link:https://www.acl.lu/fr/mobilite/diagnostic-vehicule/
Here are some examples of official rates:
Vacation Test: €39 for members / €131 for non-members
Pre-technical inspection Test: €49 for members / €131 for non-members
Second hand Test: €89 for members / €218 for non-members