The Insurance Institute for Highway Safety
The only test conducted so far was the frontal offset crash, which received the 'Good' rating for all but the head/neck portion that was categorized as 'Average.' The reason for the middle-of-the-road rating was due to the IIHS's dummy hitting its head against the steering wheel through the airbag (ouch!), and although the Institute observed the dummy striking the roof rail on rebound, it still classified the MINI's restraint system as 'Good,' since the impact was "negligible."
You can read the IIHS press release in full by clicking the 'Read' link below.