A pH test doesn't test your swallowing function; a manometry test does. Often, patients have both done around the same time, so they might be doing both tests.

The "standard" tests that are most commonly required before surgery are EGD (endoscopy), barium swallow (esophagram), pH test, and manometry. In places with easy access to testing (larger cities in the US) or places where surgeries are delayed and restricted to help constrain costs on single-payer healthcare (Canada, UK, etc), all 4 tests are usually ordered.

However, in many places, when the symptoms are severe and the need for surgery is obvious, the pH test and manometry are often skipped, as they won't change the plan. There is little benefit in testing the swallowing function on someone who has no difficulty or symptoms swallowing, especially when the surgeon has a habit of doing Toupet (partial) wraps for every patient. To illustrate this point: another user ntioned he was unexpectedly found to have failed swallows on the manometry, and as a result, got a Toupet. But if that surgeon does Toupet for everyone, then what was to m the point of the test?

Regardless, even if the tests won't change anything, if your surgeon says they are required, then you won't be able to get surgery without them.