I love the test system, and it is really useful for checking if you have memorized a certain aspect of a subject, however i noticed that currently, only a few subjects have tests built in, and others don't.
For example, health and Medicine doesn't have tests in it, and neither does some units of Biology.
Why??
Tests have come relatively recently to subjects other than Mathematics, including Biology and other Science subjects. I've noticed that High School Biology has the most comprehensive testing setup. Still, when I started studying with Khan Academy more than a year and a half ago, Biology didn't have any tests. I realize your need is likely immediate, but perhaps with a little more patience, more tests will appear in Biology.
After I posted my first reply, I discovered that Khan Academy is actively adding new material, including exercises/quizzes/tests, to Advanced Placement (AP) Biology. You can read more here:
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