As others have noted, you do it the same way EEOC and other orgs test for hiring discrimination based upon race or gender. You submit equal resumes (appropriat

As others have noted, you do it the same way EEOC and other orgs test for hiring discrimination based upon race or gender. You submit equal resumes (appropriately updated for age in this case) and see what response you get. You take a look at the company org details and do a few simple statistical runs to see how things net out. Since this is a protected class we are talking about it is a lot easier to make your case based on statistical evidence. "Gee your honor, it is purely a coincidence that all of our employees are <male/white/under-30>"...