What is Ender’s final test in chapter 4?

I think you are referring to chapter 3. They wanted to see how Ender would hanle bullies without the monitor. Mr. Wiggin brings Ender from the breakfast room to talk with the I.F. man, who questions him about his attack on Stilson. When pressed to answer why he continued kicking Ender, Ender replies that he "wanted to win all the next [fights], too. So they'd leave [him] alone," and he once again cries.