The T-shirt test is an interesting idea to see how proud you are about your organization. I don´t know if Jurgen Appelo invented the test but it was in his book “Workouts” I read about it.
You pass the test when you proudly will wear a t-shirt with your organizations logo on it. I know lots of things I can easily wear on my t-shirt. Like my favorite football team, my favorite tv-show or a role model.
I know that there are lost of hip and cool companies out here that wont have a problem to get there staff to feel for the brand on a higher level then just a regular job. But how is it at your company? Do your employs feel affinity with your brand? If not, is that a problem? Will they walk through fire for you if the situation demands it?
I don´t think that you actually need to order t-shirts to your employees and ask if the wear them. You can see this as a thought experiment when you are working with the loyalty towards the organization.
Innovators Guide To the Galaxy 