This is a question that should have two parts to it. One is whether the rock will change the tank water parameters and if that is enough to matter to you. Sop first one needs to look at what water you want to add the rocks to as where the water ends up depends on where it starts. Drop an alkaline rock in soft acidic water and you will get more change than if you drop it in hard alkaline water. So if it is a local rock that the local water runs in all the time, there is a good chance you will see no change. the two will have met in the middle a long time ago!! I use local limestone and see no change from adding rocks as the water is pumped out of limestone. So look at your water first before worry about testing?
Then ask what any testing does and why some rocks fizz. If you use muriatic acid and get a reaction, does that mean it will change your water if the PH is not as extreme as acid? Probably not! I keep in mind that my tanks are rarely filled with acid. Think of it as putting black ink in paint. If you put it in white paint, you get much more change than if you put it in black paint. So testing with acid may throw out some good rocks---unless you use acid in the tank also! Thinking judgement needed.
Second part is what on or in the nooks and crannies of the rock. That means where has it been and what it has picked up that might harm a fish. Pesticides, oil, bugs, fungus , mold or "just something" is what I want to clear, just because I don't want to deal with any unknowns later. Like washing my dishes? I feel better knowing they are clean rather than guessing so I treat them the same. I do a bleach soak as it is the standard for clearing things out of drinking water. It's in most tap water so I use it to soak anything that goes in the tank and deal with the chlorine in the same way. I dilute it and then let it gas off as it dries.