The SAT has a writing section - there is no reason you can't write code on a standardized test.

The idea is to assign low points to people who write a long function, and high points to people who write many small, self-documenting functions. Such an exam could also ask questions like "what is the cyclometric complexity of the following code?", which while not an indicator that the test taker will always write low-complexity code in a professional environment, at least indicates that the test taker is aware of maintainability metrics like cyclometric complexity - much more than can be said of programmers who mindlessly turn in 400 line functions with deeply nested conditionals.

You might not test this. Keep in mind, the bar exam, medical boards, actuarial exams, and other entrance exams aren't intended to establish competence in all areas of professional practice.

I think that the google style data structures and algorithms exams are a good case in point. Think of these like the actuarial exam for linear algebra, vector calc, and numerical analysis. These exams don't of course test everything important about being an actuary. But they do establish competence in something that can be tested. As a result, actuaries don't (to my knowledge) have to do 5 hours of whiteboard exams doing LU matrix decomposition or finding a steepest descent vector. Whereas software developers have to find all matching subtrees in a binary tree over and over (and over).

What I like about the actuarial exams is that while they are rigorous, and it helps immensely to have majored in math or something closely related, you are free to decide how to prepare for these tests. Although I like the idea of a widely recognized entrance exam, I really don't like the idea of something like the law schools putting themselves (and 200k in debt) in between an individual and the right to take the exam.