It is always important to test. Especially in planted aquariums to make sure your parameters and plant nutrition are in check to prevent algae outbreak. Gh, Ph, Kh, NO3 & PO4 are all important for plant growth and system health. Testing is also convenient if something were to go wrong. You have test kits ready to check what could be the culprit leading to your issues.
Aquarium Gallery also offers in-store testing! To help you fine tune your aquarium and provide steps on improving.