Functional Capacity Evaluation (FCE). Can anyone give info on this procedure?

Everything is now coming down to the wire and its very difficult. In an earlier post I stated my wife will soon have the opportunity to present her case in front of a judge for her SSDI. To this day we are still trying to show this judge papers received from her work that she had received 6 months sick leave with dates, amounts etc. Even with that info the judge now wants a cover letter from her former employer and stated my wife's time is running out to prove her short term disability pay was just that, not worked performed. Now her doctor, after 3 years, wants to perform a FCE on her. She may refuse to do this test because of her pain, she just wants to be left alone.