Improve validation of zip_prefixes and zips_crossing_provinces in reg…

…ion yaml files

test/worldwide/region_data_consistency_test.rb

@@ -57,6 +57,56 @@ class RegionDataConsistencyTest < ActiveSupport::TestCase
       end
     end
 
+    test "If a country has zip_prefixes, then every province has at least one prefix" do
+      Regions.all.select(&:country?).each do |country|
+        next unless country.zones&.any? { |zone| zone.zip_prefixes.present? }
+
+        zones = country.zones.select do |zone|
+          zone.zip_prefixes.blank? && # zone has no prefixes
+            zone.parents.size == 1 # zone is not a shared zone, e.g. a special territory
+        end
+
+        # IT-OT (Olbia-Tempio) no longer exists, and was absorbed into IT-SS (Sassari).
+        # We need to add proper support for "deprecation" of zones.
+        # In the mean time, we have removed all prefixes from OT intentionally.
+        if country.legacy_code == "IT"
+          zones.reject! { |z| z.legacy_code == "OT" }
+        end
+
+        # IC (Canary Islands) are not defined outside of world.yml
+        # Ceuta is listed with code EA in world.yml, but may actually be CE. TBD.
+        if country.legacy_code == "ES"
+          zones.reject! { |zone| zone.iso_code == "IC" || zone.iso_code == "EA" }
+        end
+
+        assert_empty zones, "#{country.legacy_name} has no prefix(es) for #{zones.map(&:legacy_code).join(", ")}"
+      end
+    end
+
+    test "The first province listed for each of the zips_crossing_provinces must be where that prefix resolves" do
+      Regions.all.select(&:country?).each do |country|
+        country.zips_crossing_provinces&.each do |zip, province_codes|
+          mapped_province = country.zone(zip:)
+
+          assert_equal province_codes.first, mapped_province&.legacy_code, "Expected first province code for zip #{zip}"
+        end
+      end
+    end
+
+    test "If a zip has two provinces, then both must be neighbours of each other" do
+      Regions.all.select(&:country?).each do |country|
+        country.zips_crossing_provinces&.each do |zip, province_codes|
+          neighbours = province_codes.map do |zone_code|
+            country.zone(code: zone_code)&.neighbours
+          end.flatten.uniq
+
+          province_codes.each do |zone_code|
+            assert_includes neighbours, zone_code, "zip #{zip} missing neighbour #{zone_code}"
+          end
+        end
+      end
+    end
+
     test "country codes match expected formats" do
       Regions.all.select(&:country?).each do |country|
         assert_match(/^([A-Z]{2})$/, country.iso_code, "alpha2 for #{country.legacy_name}")

test/worldwide/region_yml_consistency_test.rb

@@ -365,6 +365,39 @@ class RegionYmlConsistencyTest < ActiveSupport::TestCase
       end
     end
 
+    test "all neighbors are uppercase" do
+      Regions.all.select(&:province?).each do |province|
+        next if province.neighbors.blank?
+
+        assert province.neighbors.all?(&:upcase)
+      end
+    end
+
+    test "If A is a neighbor for B, then B must be a neighbor for A" do
+      Regions.all.select(&:country?).each do |country|
+        next if country.zones.blank?
+        next unless country.zones.any? { |zone| zone.neighbours.present? }
+
+        # Fix `neighboring_zones` data in India and Thailand
+        next if country.legacy_code == "IN" || country.legacy_code == "TH"
+
+        country.zones.each do |zone_a|
+          # Just because some zones in a country have neighbours defined doesn't mean that they all do.
+          # For example, AU-TAS is an island, so it shares no land borders with any other zone.
+          next if zone_a.neighbours.blank?
+
+          zone_a.neighbours.each do |zone_code_b|
+            zone_b = country.zone(code: zone_code_b)
+            assertion_message =
+              "Region #{country.legacy_code} zone A #{zone_a.legacy_code} zone B #{zone_b.legacy_code}"
+
+            assert_predicate zone_b.neighbours, :present?, assertion_message
+            assert_includes zone_b.neighbours, zone_a.legacy_code, assertion_message
+          end
+        end
+      end
+    end
+
     test "week_start_day is a valid value" do
       Regions.all.select(&:country?).each do |country|
         week_start_day = country.week_start_day