If your plants are healthy and doing fine, you probably don't need a soil test. Soil tests tell you about your soil. As an organic gardener, your goal is to have healthy soil to have healthy plants. So, for the average gardener, your plants are the best indicator of how healthy your soil is. One way to see if your soil is healthy is to gauge how biologically active it is.
Healthy soil is biologically active.
This means that there are lots of creatures in it that are living and breathing. A test for biological activity tests the amount of carbon dioxide, CO2, produced by your soil creatures. If this tests shows that your soil is not very biologically active, you can add compost, organic matter, and even innoculants to your soil. So now you know if your soil is alive or not. Biological enumeration is basically counting what types and how many of each type of microorganism you have in your soil.