Soil tests are not complicated - and they have their place (and we'll talk about it later) - but there's a more basic test to be done first.
It is important to recognise the type of soil you have in your garden and to understand how that can affect what you choose to plant or what will grow best in the different parts of your garden.
How to test for texture
Simply get a handful of your soil, if it is wet - roll it between your hands.
If you can roll out a sausage shape and curve the ends, then you have clay - have you considered making your own pots or garden ornaments?
If you cannot roll it because it falls to pieces then you have sand - lovely and easy to dig!
Luckily most of us will have somewhere in between(!)
Gardeners like to aim for a loam, this is part-sand, part-clay and part-humus (organic matter). You can roll your soil sample but it will collapse if you try to bend it into a curved shape.
Don't worry - whatever soil texture you have there are plants that will love to grow in it.