Evaluating a person's worth, output, and reliability is tricky business. There are so many variables to consider and compute. But no such singular set of tools exists so we listen, observe, and cobble together an opinion. Evaluating the educational worth and position of our students is subject to the very same difficulties. Single subject tests do indeed have value but that value by definition is narrow.
Tools exist, however, that can render a clearer and more in-depth portrait.
Check out the links below and please feel free to share your opinions on this very illusive but critical subject. The Case for Authentic Assessment.