Usually you are allowed Pepcid up to 3 days before the test and a simple antacid like Tums up to the day before unless you have a nasty doc like I had for my second go-round.
I had a Toupet which is basically a partial wrap Nissen. It's about
as tight as the Hill, which doesn't use the stomach for a wrap but just stitches. The tests are necessary to figure out if you have acid at all and how well you can swallow. I had the partial wrap because my swallowing is weak from polio and I wouldn't have been able to push food past a full wrap. I needed the operation because I was in an auto wreck which pushed my stomach into my chest and left me with a wide
Not fun but you'll get through it.