I never bothered with a water test. I know my water varies a little seasonally. Most do. The bulk of it is from a fairly consistent source of Mt. Springs but it's a blend of few streams too. The city has reports on all of them but not the percentages used in my blend.
Testing mashes with Precision Labs 40-70 papers (rated +/- .5) I know it dosen't have too much chalk in it, but I never have wanted to add any. That seems to be the worst thing to have a lot of in water. I've been able to make well scoring examples of pilsner and porter with very little adjustment. Some RO for bo pils, Calcium Chloride in most beers and Gypsum in a few styles (from experience I know my sulfates are very low). Light beers get some phosphoric acid in the sparge.
Maybe I'm lucky but it is just fine tuning here.
Close enough for me.