Coding "test" as part of interview?

Just a general question to anyone out there with more experience than myself.

How common is it for a potential employer to ask a job applicant to take a coding "test" for them as part of the job application?

I might understand if it were a Temp agency I suppose, trying to place a job candidate .But what about individual doctor's groups? Hospitals? other institutions where a coder would be applying for a coding position?

Any experience or stories out there to share?

Just want to know what to expect!

Coding "test" as part of interview?