test/jdk/java/util/concurrent/LinkedTransferQueue/SubclassTest.java

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/*
 * @test
 * @bug 8323659
 * @summary Ensures that the implementation of LTQ add and put methods does
 *  not call overridable offer. This test specifically asserts implementation
 *  details of LTQ. It's not that such impl details cannot change, just that
 *  such a change should be deliberately done with suitable consideration
 *  to compatibility.
 * @run testng SubclassTest
 */

import java.util.concurrent.LinkedTransferQueue;
import java.util.concurrent.TimeUnit;
import org.testng.annotations.Test;
import static org.testng.Assert.assertEquals;

@Test
public class SubclassTest {

    public void testPut() {
        var queue = new TestLinkedTransferQueue();
        queue.put(new Object());
        assertEquals(queue.size(), 1);
    }

    public void testAdd() {
        var queue = new TestLinkedTransferQueue();
        queue.add(new Object());
        assertEquals(queue.size(), 1);
    }

    public void testTimedOffer() {
        var queue = new TestLinkedTransferQueue();
        queue.offer(new Object(), 60, TimeUnit.SECONDS);
        assertEquals(queue.size(), 1);
    }

    static class TestLinkedTransferQueue extends LinkedTransferQueue<Object> {
        @Override
        public boolean offer(Object obj) {
            return false;  //  simulate fails to add the given obj
        }
    }
}