Ran tests under NeoForge 1.21.1

- Classpath scans accept the union filesystem the NeoForge 21.1 test harness mounts and skip test classes merged into it
- The 1.21.1 NeoForge server access test checks the cached world array the tick loop reads

adapters/modded-common/src/test/java/art/arcane/iris/modded/IrisModLanguageAssetsTest.java

@@ -74,7 +74,8 @@ public class IrisModLanguageAssetsTest {
     private Set<String> resourceFiles() throws Exception {
         URL resource = IrisModLanguageAssetsTest.class.getClassLoader().getResource(ROOT + "en_us.json");
         assertNotNull("Missing English mod language resource", resource);
-        assertEquals("Mod language resources must resolve to a directory on disk", "file", resource.getProtocol());
+        assertTrue("Mod language resources must resolve to a directory, got " + resource,
+                resource.getProtocol().equals("file") || resource.getProtocol().equals("union"));
         Path directory = Path.of(resource.toURI()).getParent();
         try (Stream<Path> paths = Files.list(directory)) {
             return paths

adapters/modded-common/src/test/java/art/arcane/iris/modded/ModdedClientPackageIsolationTest.java

@@ -116,7 +116,9 @@ public class ModdedClientPackageIsolationTest {
     }
 
     private static boolean isClassFile(Path path) {
-        return Files.isRegularFile(path) && path.getFileName().toString().endsWith(".class");
+        String name = path.getFileName().toString();
+        return Files.isRegularFile(path) && name.endsWith(".class")
+                && !name.endsWith("Test.class") && !name.contains("Test$");
     }
 
     private static String readAsLatin1(Path path) throws IOException {
@@ -127,7 +129,8 @@ public class ModdedClientPackageIsolationTest {
         String anchor = "/art/arcane/iris/modded/ModdedMixinAudit.class";
         URL located = ModdedClientPackageIsolationTest.class.getResource(anchor);
         assertNotNull("compiled main classes are not on the test classpath as files", located);
-        assertEquals("expected a directory classpath entry, got " + located, "file", located.getProtocol());
+        assertTrue("expected a directory classpath entry, got " + located,
+                located.getProtocol().equals("file") || located.getProtocol().equals("union"));
         Path root = Path.of(located.toURI());
         for (int depth = 0; depth < 5; depth++) {
             root = root.getParent();

adapters/neoforge/src/versions/1.21.1/test/java/art/arcane/volmlib/nativelib/minecraft26_2/neoforge/NativeNeoForgeServerAccessTest.java

@@ -0,0 +1,89 @@
+package art.arcane.volmlib.nativelib.minecraft26_2.neoforge;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.ModdedServerAccess;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.ModdedServerLevels;
+import art.arcane.volmlib.nativelib.modded.NativeLoaderOptions;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.Level;
+import org.junit.After;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.util.LinkedHashMap;
+import java.util.function.BooleanSupplier;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.doCallRealMethod;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NativeNeoForgeServerAccessTest {
+    private static final ResourceKey<Level> RUNTIME_DIMENSION =
+            ResourceKey.create(Registries.DIMENSION, ResourceLocation.fromNamespaceAndPath("irisworldgen", "runtime"));
+
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @After
+    public void forgetLevelSnapshot() {
+        ModdedServerLevels.forget();
+    }
+
+    @Test
+    public void runtimeLevelsJoinAndLeaveTheServerTickView() throws ReflectiveOperationException {
+        ModdedServerAccess access = new NativeNeoForgeLoader(
+                new NativeLoaderOptions("irisworldgen", "treefeller", BooleanSupplier::getAsBoolean)).serverAccess();
+        MinecraftServer server = serverWithLiveLevelMap();
+        ServerLevel level = mock(ServerLevel.class);
+        when(level.dimension()).thenReturn(RUNTIME_DIMENSION);
+
+        assertNull(access.putLevelIfAbsent(server, RUNTIME_DIMENSION, level));
+        assertTrue(access.hasLevel(server, RUNTIME_DIMENSION));
+        assertTrue(ticks(server, level));
+        assertSame(level, ModdedServerLevels.level(server, RUNTIME_DIMENSION));
+
+        assertSame(level, access.removeLevel(server, RUNTIME_DIMENSION));
+        assertFalse(access.hasLevel(server, RUNTIME_DIMENSION));
+        assertFalse(ticks(server, level));
+        assertNull(ModdedServerLevels.level(server, RUNTIME_DIMENSION));
+
+        assertNull(access.putLevel(server, RUNTIME_DIMENSION, level));
+        assertTrue(ticks(server, level));
+        assertSame(level, ModdedServerLevels.level(server, RUNTIME_DIMENSION));
+    }
+
+    private static MinecraftServer serverWithLiveLevelMap() throws ReflectiveOperationException {
+        MinecraftServer server = mock(MinecraftServer.class);
+        Field levels = MinecraftServer.class.getDeclaredField("levels");
+        levels.setAccessible(true);
+        levels.set(server, new LinkedHashMap<ResourceKey<Level>, ServerLevel>());
+        doCallRealMethod().when(server).getAllLevels();
+        doCallRealMethod().when(server).markWorldsDirty();
+        return server;
+    }
+
+    private static boolean ticks(MinecraftServer server, ServerLevel expected) throws ReflectiveOperationException {
+        Method worldArray = MinecraftServer.class.getDeclaredMethod("getWorldArray");
+        worldArray.setAccessible(true);
+        for (ServerLevel level : (ServerLevel[]) worldArray.invoke(server)) {
+            if (level == expected) {
+                return true;
+            }
+        }
+        return false;
+    }
+}