Since this is my first post... HELLO!
I understand there may be some shady pool companys but I have to say that the pool store (not sure if I can give the name but it's Town and Country in Phillipsburg, NJ) that installed our ABG 21"x54" (and it rocks). They use "ClearCare Expert" testing system. Since the day they installed our pool, advised on closing it last year and what to do to open it this year they've been spot on with their advice. Water is crystal clear with no issues.
I go weekly to Town and Country who tests for: Free Avaliable Chlorine, Total Chlorine, Combined Chlorine, PH, Akalinity, Calcium, Cyanuric Acid, Copper, Iron, Manganese, Nitrates, Total Solids, Phosphates, Salt and Saturation Index - for free.

Since I'm there I can pickup chems.
I use a cheapo testing kit 3 way test kit for every other day testing.
Before lumping pool stores into the same grouping as ambulance chasers I would recommend you ask about their testing process - what do they test for and how often do they recommend you test. And talk to some of their customers in the store about their experience
Got to work on my sig... 21'x54" ABG with Hayward SP1510 pump with a Hayward S180 Sand tank, using chlorine. Looking at a heatpump to extend my swimming season.