A Certified Writing Coach?

I always thought a writing coach is a writer who's had enough publication credits to be qualified. But recently I "discovered" something interesting. One day I went on a writer's blog (whose name I've forgotten), and one sentence caught my eye: "So and so (the writer's friend) is a certified writing coach." Immediately, it raised a question in my mind: How is a writing coach certified? I know how to become a certified interpreter: A would-be interpreter goes to a state-sponsored agency, takes a two-part test--oral and written--in English and the native language, if passes, he/she will become a certified interpreter. But a certified writing coach? I wonder how. It's something "new" to me. Does a would-be writing coach do the same thing an interpreter do to get certified? Going to a writing program and taking the test, if passes, he/she will become a certified writing coach?