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();