You can get basic self-test kits from anywhere but these use colour matching and are at best an indication. There are plenty of specialist firms online who will send you sample pots. Take samples from several different areas of your land, and make sure you dig into the real soil. You will get a detailed analysis with recommendations.
In any case it's worthwhile digging some one foot cube holes just to look at the soil structure and to smell the soil. You will learn a lot. It's part of the absolute truth that the best fertiliser is the farmer's boot.