They can't tell whether you open a new window, but they have various built-in safeguards against using outside resources, including collaborating with other test-takers. In order to participate in their program, you have to use their software, which is specially designed to detect and prevent different types of cheating. In addition, the timing of each question is short enough that you will not have time to use other resources and still finish the test. You have to log in at a certain time, and the software will export your results when you reach the time limit, whether or not you have finished. There are log-in keys and passwords, and they scramble the order of questions so that students can't sit at adjacent computers and say, "What did you get on #6?" Also if two tests have close to the same log-in times and the same pattern of answers, the software will detect it. Finally, they monitor YA and other answer sites for questions just like the one you just asked, and can obtain your IP address. They know every trick in the book, including many you haven't even dreamed of. And yes, they are going to check, because if you cheat it undermines the value of their program.