One problem with performance tests is that if they actually tested the current law of a state as it relates to a specific subject, bar applicants who attended law school in that state and took a course focused on that state's law on that subject might have an unfair advantage over applicants who did not. In other words, the performance test would be testing applicants' understanding of current state law, as opposed to their lawyering skills. To mitigate that advantage, performance tests normally use the law of a fictional state, and its law as provided in the test materials usually has subtle differences from the law in the real world in order to reduce the advantage of having already studied that subject matter in law school. This forces applicants to demonstrate their ability to interpret and apply the law as they find it, rather than the law they already know.