Thanks!(As a quick review, for anyone who may stumble on this thread while frantically googling: Civ 4's official rules are that you may trade on any river that remains within your territory or in neutral territory. Civ 4 BTS amended this rule to require sailing in order to trade along rivers in neutral territory [you can still trade within your own territory along rivers without the sailing technology]. This rule change makes the Civilopedia entries confusing, as you need to read the entry on BTS rule changes in order to get the full rule, and the City Network rule section is incomplete without it
Always appreciate fine testing.
Code just makes my eyes glaze over, but I can follow good tests.
City network questions are not a huge deal, but they can be important when trying to snag that iron or marble out in the hinterlands.
Or if a city needs to be isolated to churn out Warriors.