Lol, well giving the exam is something left for Prometric 😛.
In all honesty, in all of the vernacular I've heard in college, pop culture, literature, books, and anything of prominence I've never heard of taking a test as "writing" it. Maybe this is region-specific, but in California I've never heard of this.
Is there anyone whose heard this phrase in common usage where one can write a test? And if so, what region are you from?
Does one take trips? or take orders? Or take their time? The word take is established in this context throughout the English language. "Writing" is not, which is why I find it a peculiar saying. Especially since nothing about taking the MCAT meets the traditional definitions of the word (creating a work, or the act of typing) except for the actual writing section.