How do I test the soil before gardening?

You can buy a soil test kit.

https://www.google.com/search?q=soil+ph+test+kit&source=univ&tbm=shop&tbo=u&sa=X&ved=2ahUKEwj9ytmf_vflAhUP2qwKHR9lDF0Qsxh6BAgPECg&biw=1536&bih=740

There are kits you can get at your local nursery. Some need to be sent off for testing.

The only way is to buy a kit. It will tell you whether your soil is acid or alkeline which will help you to choose the correct plants for your soil. If you want plants that will not thrive in your soil try buying the right compost and growing them in a pot.

I don't test mine very often, but use one of the spike type meters.