Where can students take the Calculus 3 test to get college credits without taking the class? If you can't get college credits that way, then can someone just take the test and let them give you the score and paper says that you understand the course material for that subject? If you need to pay for this test, how much will they charge you? Consider someone who lives in Los Angeles.
Unfortunately, there is no way to take a test to receive credit for Calc 3. The common AP level calculus tests can be taken without taking the course as you can register for them separately through your high school or through college board. However, the AP level calculus is equivalent to introductory level calculus in college (Calc 1 or 2).
If you are already in college, you might want to talk to someone in the math department to see if they can administer a department test for you. Even then I would think that they will allow you to "jump" to the next level of mathematics and not simply give you credit for Calc 3. Still, nothing is set in stone and each college has its own policy with such matters. The best advice is to simply ask!