test: characterize multipart mod lifecycle

Pin the Scala singleton identity and FML event surface before the Java port.

src/test/java/codechicken/multipart/handler/MultipartModCharacterizationTest.java

@@ -0,0 +1,79 @@
+package codechicken.multipart.handler;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.Arrays;
+import java.util.Set;
+import java.util.TreeSet;
+
+import org.junit.jupiter.api.Test;
+import org.objectweb.asm.Type;
+
+import codechicken.multipart.Tags;
+import cpw.mods.fml.common.Mod;
+
+class MultipartModCharacterizationTest {
+
+    private static final Set<String> EVENT_METHODS = new TreeSet<>(
+            Arrays.asList(
+                    "beforeServerStart(Lcpw/mods/fml/common/event/FMLServerAboutToStartEvent;)V",
+                    "init(Lcpw/mods/fml/common/event/FMLInitializationEvent;)V",
+                    "postInit(Lcpw/mods/fml/common/event/FMLPostInitializationEvent;)V",
+                    "preInit(Lcpw/mods/fml/common/event/FMLPreInitializationEvent;)V",
+                    "serverStopped(Lcpw/mods/fml/common/event/FMLServerStoppedEvent;)V"));
+
+    @Test
+    void keepsBothAnnotatedSingletonTypesAndLifecycleMethods() throws Exception {
+        assertModType(MultipartMod.class, true);
+        assertModType(MultipartMod$.class, false);
+
+        assertEquals(0, MultipartMod.class.getFields().length);
+        Field module = MultipartMod$.class.getField("MODULE$");
+        assertSame(MultipartMod$.class, module.getType());
+        assertTrue(Modifier.isStatic(module.getModifiers()));
+        assertTrue(Modifier.isFinal(module.getModifiers()));
+        assertSame(MultipartMod$.MODULE$, module.get(null));
+    }
+
+    @Test
+    void packetHandlerChannelUsesTheModCompanionIdentity() throws Exception {
+        assertSame(MultipartMod$.MODULE$, new MultipartPH().channel());
+        assertSame(MultipartMod$.class, MultipartPH.class.getDeclaredMethod("channel").getReturnType());
+        assertSame(MultipartMod$.class, MultipartPH.class.getDeclaredField("channel").getType());
+    }
+
+    private static void assertModType(Class<?> type, boolean staticMethods) {
+        assertTrue(Modifier.isPublic(type.getModifiers()));
+        assertTrue(Modifier.isFinal(type.getModifiers()));
+        assertEquals(EVENT_METHODS, publicMethodSignatures(type));
+
+        Mod mod = type.getAnnotation(Mod.class);
+        assertEquals("ForgeMultipart", mod.modid());
+        assertEquals("Forge Multipart", mod.name());
+        assertEquals("[1.7.10]", mod.acceptedMinecraftVersions());
+        assertEquals(Tags.VERSION, mod.version());
+        assertEquals("scala", mod.modLanguage());
+
+        for (Method method : type.getDeclaredMethods()) {
+            if (Modifier.isPublic(method.getModifiers())) {
+                assertTrue(method.isAnnotationPresent(Mod.EventHandler.class));
+                assertEquals(staticMethods, Modifier.isStatic(method.getModifiers()));
+            }
+        }
+    }
+
+    private static Set<String> publicMethodSignatures(Class<?> type) {
+        Set<String> signatures = new TreeSet<>();
+        for (Method method : type.getDeclaredMethods()) {
+            if (Modifier.isPublic(method.getModifiers())) {
+                signatures.add(method.getName() + Type.getMethodDescriptor(method));
+            }
+        }
+        return signatures;
+    }
+}