Different stores might test for different things, some are not as important as others, or you might be able to ask them to test for something specific. You will really want your own test kit at some point if you plan on sticking with the hobby. When things go wrong, you want to be able to test the water and take action, not go to the store every other day while you're having problems. If you go with any fish to cycle the tank, prepare for daily water changes, possibly 50% or more. If not the fish will most likely die and you will be back at square one in terms of cycling. Unless of course you run out and buy more fish right away (but that would be a waste of time and money). Also, using a fish as a guinea pig to test the safeness of the water isn't really all that reliable. Some fish can withstand worse water conditions than others, and depending on just how bad the water is, the fish might live for several weeks without alot of obvious problems