Add mixins to forge 1206 test

src/test/groovy/net/fabricmc/loom/test/integration/forge/Forge1206Test.groovy

@@ -34,7 +34,7 @@ import static org.gradle.testkit.runner.TaskOutcome.SUCCESS
 
 class Forge1206Test extends Specification implements GradleProjectTestTrait {
 	@Unroll
-	def "build #mcVersion #neoforgeVersion #mappings #patches"() {
+	def "build #mcVersion #forgeVersion #mappings #patches"() {
 		if (Integer.valueOf(System.getProperty("java.version").split("\\.")[0]) < 21) {
 			println("This test requires Java 21. Currently you have Java ${System.getProperty("java.version")}.")
 			return
@@ -43,7 +43,7 @@ class Forge1206Test extends Specification implements GradleProjectTestTrait {
 		setup:
 		def gradle = gradleProject(project: "forge/1206", version: DEFAULT_GRADLE)
 		gradle.buildGradle.text = gradle.buildGradle.text.replace('@MCVERSION@', mcVersion)
-				.replace('@FORGEVERSION@', neoforgeVersion)
+				.replace('@FORGEVERSION@', forgeVersion)
 				.replace('MAPPINGS', mappings) // Spotless doesn't like the @'s
 				.replace('PATCHES', patches)
 
@@ -54,7 +54,7 @@ class Forge1206Test extends Specification implements GradleProjectTestTrait {
 		result.task(":build").outcome == SUCCESS
 
 		where:
-		mcVersion | neoforgeVersion | mappings | patches
+		mcVersion | forgeVersion    | mappings | patches
 		'1.20.6'  | '1.20.6-50.1.3' | 'loom.officialMojangMappings()' | ''
 	}
 }

src/test/resources/projects/forge/1206/build.gradle

@@ -18,6 +18,17 @@ group = project.maven_group
 def mcVersion = "@MCVERSION@"
 def forgeVersion = "@FORGEVERSION@"
 
+
+loom {
+	forge {
+		mixinConfig "examplemod.mixins.json"
+	}
+
+	afterEvaluate {
+		assert mixin.useLegacyMixinAp.get() == false
+	}
+}
+
 repositories {
 	// Add repositories to retrieve artifacts from in here.
 	// You should only use this when depending on other mods because

src/test/resources/projects/forge/1206/src/main/java/com/example/examplemod/mixin/ExampleModMixin.java

@@ -0,0 +1,15 @@
+package com.example.examplemod.mixin;
+
+import net.minecraft.client.Minecraft;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(Minecraft.class)
+public class ExampleModMixin {
+	@Inject(method = "<clinit>", at = @At("HEAD"))
+	private static void initInject(CallbackInfo info) {
+		System.out.println("Hello from the example mod mixin!");
+	}
+}

src/test/resources/projects/forge/1206/src/main/resources/examplemod.mixins.json

@@ -0,0 +1,14 @@
+{
+  "required": true,
+  "minVersion": "0.8",
+  "package": "com.example.examplemod.mixin",
+  "compatibilityLevel": "JAVA_17",
+  "mixins": [
+  ],
+  "client": [
+    "ExampleModMixin"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}