GREY'S ANATOMY - "Testing 1-2-3" - The interns take the biggest test of their careers, their first-year medical exams, as the residents attend to three injured mountain climbers. Meanwhile Callie's suspicions of George and Izzie grow, and Cristina struggles to write her wedding vows, on "Grey's Anatomy," THURSDAY, MAY 10 (9:00-10:01 p.m., ET) on the ABC Television Network. (ABC/SCOTT GARFIELD) CHANDRA WILSON, T.R. KNIGHT