Test kit should be kept inside. Climate controlled.
Liquid chlorine is best kept in an area of normal temperatures. Where I live, indoors.
Muriatic acid should be kept in a plastic receptacle, I use a 20 gallon trash can with lid, outside. By itself. Away from metals.
I keep my testing kit(s) stored inside, in a dark, cool place.
My chlorine lives in the garage, and the one in current use lives in a non out near the pool, in the shade.
Other chemicals live in the house -- borax, baking soda, phDown, that sort of thing. I'm afraid of muriatic acid, so I use dry acid. Never need it very often, so I don't worry about the sulfide buildup.