There are a lot of tests out there to help you find your Ayurvedic dosha. It’s a good idea to take several tests and look for consistencies. To be absolutely sure though you must find a good Ayurvedic practitioner and have them help you determine your Prakruti and Vikruti so that you can start making wiser choices for yourself. Prakruti is your natural born constitution. Vikruti is your current constitution. Ayurveda aims to get your body and your mind from Vikruti back to Prakruti.
One of my favorite quizzes can be found here.