There are a few structured interviews which can be used to assess for ADHD, though they're not widely used. A lot of providers will request you undergo neuropsychological testing which doesn't test for ADHD and which is not an accurate diagnostic tool for ADHD concerns. Some of the best tools out there are the ADHD Adult Self Report Screening Questionnaire and other rating scales that note impairment in functional areas of life.

The best evaluation for ADHD is a full interview with additional collateral information if possible. That's the best way to achieve a diagnosis. Many providers will feel uncomfortable diagnosing ADHD either due to being unfamiliar with it or being biased in some way. There's a lot of stigma around ADHD as well as around stimulant medication, so providers will often pass the buck to someone else to decide.

So, there is no specific "test" that you take to prove that you have ADHD. There are structured interviews that providers can use which can help diagnose ADHD, but the most important thing is a good evaluation based on the clinical interview, gathering a good history, and trying to obtain an understanding of areas where you struggle such as work, school, or social settings. Often times people do go to specialists to get assessed, though they can be hard to find and often have long waits to be seen.