Loader spawn position check

- The modded chunk generator hands VolmLib the bound loader for chunk-generation creature checks
- Each loader build tests its spawn position check: Forge and NeoForge fire MobSpawnEvent.PositionCheck and honor a denial, Fabric applies the vanilla rule and obstruction checks

adapters/neoforge/src/test/java/art/arcane/volmlib/nativelib/minecraft26_2/neoforge/NativeNeoForgeSpawnPositionTest.java

@@ -0,0 +1,58 @@
+package art.arcane.volmlib.nativelib.minecraft26_2.neoforge;
+
+import art.arcane.volmlib.nativelib.modded.NativeLoaderOptions;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.entity.EntitySpawnReason;
+import net.minecraft.world.entity.Mob;
+import net.minecraft.world.level.ServerLevelAccessor;
+import net.neoforged.neoforge.common.NeoForge;
+import net.neoforged.neoforge.event.entity.living.MobSpawnEvent;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.BooleanSupplier;
+import java.util.function.Consumer;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NativeNeoForgeSpawnPositionTest {
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void chunkGenerationSpawnsFireThePositionCheckEventAndHonorItsDenial() {
+        NativeNeoForgeLoader loader = new NativeNeoForgeLoader(
+                new NativeLoaderOptions("irisworldgen", "treefeller", BooleanSupplier::getAsBoolean));
+        ServerLevelAccessor level = mock(ServerLevelAccessor.class);
+        Mob mob = mock(Mob.class);
+        when(mob.checkSpawnRules(level, EntitySpawnReason.CHUNK_GENERATION)).thenReturn(true);
+        when(mob.checkSpawnObstruction(level)).thenReturn(true);
+        AtomicBoolean deny = new AtomicBoolean(true);
+        AtomicReference<EntitySpawnReason> observed = new AtomicReference<>();
+        Consumer<MobSpawnEvent.PositionCheck> listener = (MobSpawnEvent.PositionCheck event) -> {
+            if (event.getEntity() == mob && deny.get()) {
+                observed.set(event.getSpawnType());
+                event.setResult(MobSpawnEvent.PositionCheck.Result.FAIL);
+            }
+        };
+        NeoForge.EVENT_BUS.addListener(MobSpawnEvent.PositionCheck.class, listener);
+        try {
+            assertFalse(loader.checkSpawnPosition(mob, level, EntitySpawnReason.CHUNK_GENERATION));
+            assertEquals(EntitySpawnReason.CHUNK_GENERATION, observed.get());
+            deny.set(false);
+            assertTrue(loader.checkSpawnPosition(mob, level, EntitySpawnReason.CHUNK_GENERATION));
+        } finally {
+            NeoForge.EVENT_BUS.unregister(listener);
+        }
+    }
+}