GREY'S ANATOMY - &quot;Testing 1-2-3&quot; - 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 &quot;Grey's Anatomy,&quot; THURSDAY, MAY 10 (9:00-10:01 p.m., ET) on the ABC Television Network. (ABC/SCOTT GARFIELD)CHANDRA WILSON, T.R. KNIGHT, JUSTIN CHAMBERS, SANDRA OH, KATHERINE HEIGL