I realize the Constitution’s only requirement for Presidency is to be a citizen 35 years of age or older, but I think it’d be possible to create enough public pressure to make it a de facto requirement without having to go through an amendment process. Theoretically, candidates could skip out on it, but it would make them look bad, just like refusing to hold a debate with their opponent would also harm them too much to be worthwhile.
Set up a bipartisan commission, similar in style to the Commission on Presidential Debates to create the test. Composed equally of Republicans and Democrats.
The aptitude test will be on the candidates knowledge of current events, the economy, world affairs, analytical and logical reasoning, and the U.S Constitution.
Neither candidate will have advance knowledge of what specifically will be on the test. They will have to show up in person and fill out the forms all by themselves.