Fix VillagerTypeTestMod not working (#10426)

src/main/java/net/minecraftforge/common/extensions/IForgeGameTestHelper.java

@@ -5,6 +5,7 @@
 
 package net.minecraftforge.common.extensions;
 
+import java.util.Objects;
 import java.util.UUID;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
@@ -61,6 +62,13 @@ public interface IForgeGameTestHelper {
             throw new GameTestAssertException(message.get());
     }
 
+    /** Backported from 1.20.6 */
+    default <N> void assertValueEqual(N expected, N actual, String name) {
+        if (!Objects.equals(expected, actual)) {
+            throw new GameTestAssertException("Expected " + name + " to be " + expected + ", but was " + actual);
+        }
+    }
+
     // Backported from 1.20.6
     default Player makeMockPlayer(final GameType p_333981_) {
         return new Player(this.self().getLevel(), BlockPos.ZERO, 0.0F, new GameProfile(UUID.randomUUID(), "test-mock-player")) {

src/test/java/net/minecraftforge/debug/gameplay/villager/VillagerTypeTestMod.java

@@ -14,6 +14,7 @@ import net.minecraft.world.entity.EntityType;
 import net.minecraft.world.entity.npc.Villager;
 import net.minecraft.world.entity.npc.VillagerTrades;
 import net.minecraft.world.entity.npc.VillagerType;
+import net.minecraft.world.item.Item;
 import net.minecraft.world.item.Items;
 import net.minecraft.world.level.biome.Biome;
 import net.minecraft.world.level.biome.Biomes;
@@ -24,6 +25,7 @@ import net.minecraftforge.gametest.GameTestHolder;
 import net.minecraftforge.registries.DeferredRegister;
 import net.minecraftforge.registries.RegistryObject;
 import net.minecraftforge.test.BaseTestMod;
+import net.minecraftforge.unsafe.UnsafeHacks;
 
 import java.util.Map;
 
@@ -58,17 +60,17 @@ public class VillagerTypeTestMod extends BaseTestMod {
         helper.succeed();
     }
 
-    /** Test verifies NPE not thrown when looking up a villager type in the trade that doesn't contain that type.*/
+    /** Test verifies NPE not thrown when looking up a villager type in the trade that doesn't contain that type. */
     @GameTest(template = "forge:empty3x3x3")
     public static void emeralds_for_villager_type(GameTestHelper helper) {
-        var trade = new VillagerTrades.EmeraldsForVillagerTypeItem(1, 12, 30, Map.of(TEST_VILLAGER_TYPE.get(), Items.DIRT));
+        var trade = unsafeCreateTrade(1, 12, 30, Map.of(TEST_VILLAGER_TYPE.get(), Items.DIRT));
         var rnd = helper.getLevel().getRandom();
 
         // Should be a successful trade for dirt for our test villager
         var test = new Villager(EntityType.VILLAGER, helper.getLevel(), TEST_VILLAGER_TYPE.get());
         var test_offer = trade.getOffer(test, rnd);
         helper.assertFalse(test_offer == null, "Failed to retreive trade value for test profession");
-        helper.assertValueEqual(test_offer.getItemCostA().itemStack().getItem(), Items.DIRT, "Offer did not return the expected item");
+        helper.assertValueEqual(test_offer.getCostA().getItem(), Items.DIRT, "Offer did not return the expected item");
 
         var plains = new Villager(EntityType.VILLAGER, helper.getLevel(), VillagerType.PLAINS);
         // This will NPE on unpatched code, we need to test that it returns null correctly
@@ -77,4 +79,16 @@ public class VillagerTypeTestMod extends BaseTestMod {
 
         helper.succeed();
     }
+
+    private static VillagerTrades.ItemListing unsafeCreateTrade(int cost, int maxUses, int villagerXp, Map<VillagerType, Item> trades) {
+        try {
+            var ctor = Class
+                .forName("net.minecraft.world.entity.npc.VillagerTrades$EmeraldsForVillagerTypeItem")
+                .getDeclaredConstructor(int.class, int.class, int.class, Map.class);
+            UnsafeHacks.setAccessible(ctor);
+            return (VillagerTrades.ItemListing) ctor.newInstance(cost, maxUses, villagerXp, trades);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
 }