I've been fielding questions about the CASPER test recently. The examination is aimed to assess empathy, emotional intelligence, and professionalism. CASPER is multifaceted, and I would recommend you look here for information about the components. There are some useful, instructive videos on the site.
Of note, CASPER is not required for all US medical schools, so it's important to determine whether you need to take the examination at all. If so, when you have to take the test is dependent on different institutions' due dates (which is frustrating).
If you do need to take the examination, please plan to prepare even if you feel you have a high emotional quotient. I've had some applicants in the past take the CASPER without reviewing in advance, and many of them were surprised by their suboptimal performance. Applicants cannot retake in an admissions cycle.
The FAQ page here is helpful.
