IBM used to have Test 486 "Object-Oriented Analysis and Design with UML". I passed it in 2000 in Bangalore, on the second attempt. Actually, I almost passed it on the first attempt too. It's an interesting story :) I took a test in Almaty after a couple of weeks of preparation. I didn't have any special books or exam crams, so had to study with Booch's OOA&D monograph and other similar sources. When the exam started, it was apparent that the content is very different from what I expected it to be. It demoralized me, so I gave up before the exam ended. It was big surprise when the printout showed that I was just 2-3 points from passing grade! It was a good lesson to me for the future: never give up! While in India I spent a few more days of studying obscure concepts of OOP and passed the test with a comfortable margin this time. IBM retired this test, and has created two new tests instead: Test 833 Object Oriented Analysis and Design - Part 1 (Analysis) and Test 834 Part2 (Design).
I was in OO already a few years in 2000, but as it usually happens while preparing to the test had to learn a couple of new things and somewhat systemized my knowledge and experience. It was very useful.