We know it seems counter-intuitive that your testing would be more accurate than a pool store, but it's true. Your testing will be consistent, performed by someone who is highly motivated to keep your pool clear/safe at the lowest cost, performed by someone who is not hurried to get to the next customer, performed by someone who is not concerned about making a sale to make their store manager happy, and so on.
The test kits we recommended are complete and have the industry standard Taylor branded reagents which are highly accurate within the tolerances required to maintain a clear and safe pool. So fear not, test yourself and save on chemical costs. And most importantly, do not compare your results to a pool store's. Resist the urge! If you have questions, we are ALWAYS here, practically 24/7, and regardless of worldwide pandemics, to answer your testing (and other pool) questions.