Added a tundra fringe and ragged polar ice edges to the map generator

tests/data_test.js

@@ -6,6 +6,7 @@ import {
   GOVERNMENTS,
   TECHNOLOGIES,
   TRAINABLE_UNIT_IDS,
+  TERRAIN_TILES,
   protoUnitById,
   buildingById,
   governmentById,
@@ -151,4 +152,14 @@ export class DataTest extends TestCase {
     this.assertApprox(effectValue(effect, 3), 30);
     this.assertEqual(effectValue(effect, 0), 0);
   }
+
+  test_tundra_is_rocky_but_flat_and_unproductive() {
+    const tundra = TERRAIN_TILES.find((t) => t.terrainType === "Tundra");
+    this.assertNotNull(tundra, "tundra exists");
+    this.assertEqual(tundra.terrainClass, "Land", "tundra is land");
+    this.assertEqual(tundra.defenseBonus, 0, "tundra stays flat");
+    this.assertApprox(tundra.populationMultiplier, 0.05, 1e-9);
+    this.assertApprox(tundra.gdpMultiplier, 0.2, 1e-9);
+    this.assertApprox(tundra.movementCostMultiplier, 2.0, 1e-9);
+  }
 }