Configure classpath groups for test task.

Closes #1192

src/main/java/net/fabricmc/loom/configuration/CompileConfiguration.java

@@ -26,6 +26,7 @@
 
 import static net.fabricmc.loom.util.Constants.Configurations;
 
+import java.io.File;
 import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.nio.charset.StandardCharsets;
@@ -34,6 +35,7 @@
 import java.time.Duration;
 import java.util.Optional;
 import java.util.function.Consumer;
+import java.util.stream.Collectors;
 
 import javax.inject.Inject;
 
@@ -47,6 +49,7 @@
 import org.gradle.api.tasks.TaskContainer;
 import org.gradle.api.tasks.compile.JavaCompile;
 import org.gradle.api.tasks.javadoc.Javadoc;
+import org.gradle.api.tasks.testing.Test;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.api.InterfaceInjectionExtensionAPI;
@@ -128,6 +131,7 @@ public void run() {
 			}
 
 			configureDecompileTasks(configContext);
+			configureTestTask();
 		});
 
 		finalizedBy("eclipse", "genEclipseRuns");
@@ -244,6 +248,26 @@ private void configureDecompileTasks(ConfigContext configContext) {
 				.afterEvaluation();
 	}
 
+	private void configureTestTask() {
+		final LoomGradleExtension extension = LoomGradleExtension.get(getProject());
+
+		if (extension.getMods().isEmpty()) {
+			return;
+		}
+
+		getProject().getTasks().named(JavaPlugin.TEST_TASK_NAME, Test.class, test -> {
+			String classPathGroups = extension.getMods().stream()
+					.map(modSettings ->
+							SourceSetHelper.getClasspath(modSettings, getProject()).stream()
+									.map(File::getAbsolutePath)
+									.collect(Collectors.joining(File.pathSeparator))
+					)
+					.collect(Collectors.joining(File.pathSeparator+File.pathSeparator));;
+
+			test.systemProperty("fabric.classPathGroups", classPathGroups);
+		});
+	}
+
 	private LockFile getLockFile() {
 		final LoomGradleExtension extension = LoomGradleExtension.get(getProject());
 		final Path cacheDirectory = extension.getFiles().getUserCache().toPath();

src/test/groovy/net/fabricmc/loom/test/integration/FabricAPITest.groovy

@@ -44,7 +44,7 @@ class FabricAPITest extends Specification implements GradleProjectTestTrait {
 		setup:
 		def gradle = gradleProject(
 				repo: "https://github.com/FabricMC/fabric.git",
-				commit: "41bc64cd617f03d49ecc4a4f7788cb65d465415c",
+				commit: "70277babddfaf52ee30013af94764da19473b3b1",
 				version: version,
 				patch: "fabric_api"
 				)
@@ -58,7 +58,7 @@ class FabricAPITest extends Specification implements GradleProjectTestTrait {
 				""".stripIndent()
 		}
 
-		def minecraftVersion = "1.21"
+		def minecraftVersion = "1.21.4-pre3"
 		def server = ServerRunner.create(gradle.projectDir, minecraftVersion)
 				.withMod(gradle.getOutputFile("fabric-api-999.0.0.jar"))
 

src/test/resources/patches/fabric_api.patch

@@ -1,15 +1,6 @@
 diff --git a/build.gradle b/build.gradle
---- a/build.gradle	(revision 41bc64cd617f03d49ecc4a4f7788cb65d465415c)
-+++ b/build.gradle	(date 1718312645477)
-@@ -13,7 +13,7 @@
-
- def ENV = System.getenv()
-
--version = project.version + "+" + (ENV.GITHUB_RUN_NUMBER ? "" : "local-") + getBranch()
-+version = "999.0.0"
- logger.lifecycle("Building Fabric: " + version)
-
- def metaProjects = [
+--- a/build.gradle	(revision 70277babddfaf52ee30013af94764da19473b3b1)
++++ b/build.gradle	(date 1732874605816)
 @@ -34,24 +34,7 @@
  import org.apache.commons.codec.digest.DigestUtils
 
@@ -34,5 +25,25 @@ diff --git a/build.gradle b/build.gradle
 -	return version + "+" + latestCommits.get(0).id.substring(0, 8) + DigestUtils.sha256Hex(project.rootProject.minecraft_version).substring(0, 2)
 +	return "999.0.0"
  }
- 
+
  def getBranch() {
+@@ -247,19 +230,6 @@
+
+ 	test {
+ 		useJUnitPlatform()
+-
+-		afterEvaluate {
+-			// See: https://github.com/FabricMC/fabric-loader/pull/585
+-			def classPathGroups = loom.mods.stream()
+-					.map { modSettings ->
+-						SourceSetHelper.getClasspath(modSettings, getProject()).stream()
+-								.map(File.&getAbsolutePath)
+-								.collect(Collectors.joining(File.pathSeparator))
+-					}
+-					.collect(Collectors.joining(File.pathSeparator+File.pathSeparator))
+-
+-			systemProperty("fabric.classPathGroups", classPathGroups)
+-		}
+ 	}
+
+ 	tasks.withType(ProcessResources).configureEach {