I went voluntarily for a chemical dependency assessment, which was offered to me as an option by a marriage counselor.
For me it was filling in some forms and questionnaires, then answering some questions in an interview type of conversation, then discussion of the results. Interesting opportunity to shine a light on a set of patterns in my life which I had been minimizing or denying.
Depending on what you want, that can be the end, or you can be referred for treatment or rehab if you choose.
It's crucial to be honest - otherwise you are wasting your time.