He is taking the tests to determine the level of his intelligence and to determine if he has the right psychological profile to be used in the study. Alice has recommended Charlie because unlike others with his low IQ, he is a positive guy and eager to learn. The team gives him ink blot tests, which he cannot even do because he is a literal thinker and sees nothing on the page but a blot of ink. He is unable to think abstractly at first. They also give him tests to see if he can out-think Algernon and escape from a maze. The tests are given prior to the operation so that the research team can have a baseline with which to compare after Charlie's operation. The only way they can measure his growth is to compare how he did on the tests before and after the operation.