GH-4673 Add failing test for Cleaner-based auto shutdown in SPARQLRepository

Author: hmottestad

core/repository/sparql/src/test/java/org/eclipse/rdf4j/repository/sparql/SPARQLRepositoryCleanerTest.java

@@ -0,0 +1,72 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Eclipse RDF4J contributors.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Distribution License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *******************************************************************************/
+package org.eclipse.rdf4j.repository.sparql;
+
+import static org.assertj.core.api.Assertions.fail;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import org.eclipse.rdf4j.repository.RepositoryConnection;
+import org.eclipse.rdf4j.repository.RepositoryException;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Verifies that a SPARQLRepository performs internal shutdown when it becomes unreachable.
+ *
+ * <p>
+ * This test intentionally does not call {@code repository.shutDown()}. It expects the repository to arrange for its
+ * internal {@code shutDownInternal()} to run when the object is no longer reachable (e.g., by using Java 9 Cleaner).
+ * </p>
+ */
+public class SPARQLRepositoryCleanerTest {
+
+	@Test
+	void autoShutdownOnUnreachable() throws Exception {
+		CountDownLatch shutdownInvoked = new CountDownLatch(1);
+
+		runRepo(shutdownInvoked);
+
+		// Encourage GC and wait briefly for cleaner to run
+		boolean observed = false;
+		for (int i = 0; i < 20 && !observed; i++) {
+			System.gc();
+			System.runFinalization();
+			observed = shutdownInvoked.await(250, TimeUnit.MILLISECONDS);
+		}
+
+		if (!observed) {
+			fail("Expected shutDownInternal() to be invoked when SPARQLRepository became unreachable");
+		}
+	}
+
+	private static void runRepo(CountDownLatch shutdownInvoked) {
+		// Create a repository instance that signals when shutDownInternal() is invoked
+		SPARQLRepository repo = new SPARQLRepository("http://example.org/sparql") {
+			@Override
+			protected void shutDownInternal() throws RepositoryException {
+				try {
+					super.shutDownInternal();
+				} finally {
+					shutdownInvoked.countDown();
+				}
+			}
+		};
+
+		// Exercise minimal usage without hitting the network
+		try (RepositoryConnection conn = repo.getConnection()) {
+			// no-op
+		}
+
+		// Drop strong reference and ask GC to collect
+		repo = null;
+	}
+}