I;d give them a blank piece of paper and ask them to generate their own test. And then answer it :)

David, this is an interesting topic that I've been thinking about for a while (although perhaps from a different angle). There are a few ways to interpret your question, so it'd be useful to understand where are you coming from:

1. What tests are most appropriate/valid/veridical to measure their creativity?

2. Given that they are creative, and a diverse group, what problems should we be giving them to take advantage of their skills?

3. What are the criteria for the type of tasks that researchers should be applying to creative practitioners?

4. Or since you are talking about groups of 'creative geniuses', perhaps the scales or tasks that you are interested are related to communication and collaboration?

5. Somewhere else.

I'm very interested in #3 given the apparent 'chaos' in how problem tasks are defined and applied in the literature. Slightly interested in #2 and #4, and not really interested in #1 at all.

In my teaching, I formulate very general and open-ended 'briefs' to learners, something like "How would you make the world better?", and it tends to work quite well in terms of creativity. The Dyson Foundation seems to agree, their recent design competition asked people to "Design something that solves a problem". Have a look: http://www.jamesdysonaward.org/the-brief/

http://www.jamesdysonaward.org/the-brief/