Java

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/*
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 * Copyright (C) 2011 The Guava Authors
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 * http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.google.common.testing;
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import static com.google.common.truth.Truth.assertThat;
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import static org.junit.Assert.assertThrows;
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import com.google.common.testing.GcFinalization.FinalizationPredicate;
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import com.google.common.util.concurrent.SettableFuture;
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import java.lang.ref.WeakReference;
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import java.util.WeakHashMap;
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import java.util.concurrent.CountDownLatch;
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import java.util.concurrent.atomic.AtomicBoolean;
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import junit.framework.TestCase;
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import org.checkerframework.checker.nullness.qual.Nullable;
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/**
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 * Tests for {@link GcFinalization}.
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 *
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 * @author Martin Buchholz
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 * @author mike nonemacher
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 */
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@AndroidIncompatible // depends on details of gc
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public class GcFinalizationTest extends TestCase {
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  // ----------------------------------------------------------------
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  // Ordinary tests of successful method execution
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  // ----------------------------------------------------------------
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  public void testAwait_countDownLatch() {
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    final CountDownLatch latch = new CountDownLatch(1);
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    Object unused =
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        new Object() {
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          @SuppressWarnings({"removal", "Finalize"}) // b/260137033
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          @Override
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          protected void finalize() {
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            latch.countDown();
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          }
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        };
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    unused = null; // Hint to the JIT that unused is unreachable
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    GcFinalization.await(latch);
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    assertEquals(0, latch.getCount());
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  }
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  public void testAwaitDone_future() {
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    final SettableFuture<@Nullable Void> future = SettableFuture.create();
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    Object unused =
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        new Object() {
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          @SuppressWarnings({"removal", "Finalize"}) // b/260137033
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          @Override
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          protected void finalize() {
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            future.set(null);
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          }
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        };
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    unused = null; // Hint to the JIT that unused is unreachable
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    GcFinalization.awaitDone(future);
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    assertTrue(future.isDone());
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    assertFalse(future.isCancelled());
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  }
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  public void testAwaitDone_future_cancel() {
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    final SettableFuture<@Nullable Void> future = SettableFuture.create();
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    Object unused =
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        new Object() {
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          @SuppressWarnings({"removal", "Finalize"}) // b/260137033
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          @Override
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          protected void finalize() {
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            future.cancel(false);
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          }
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        };
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    unused = null; // Hint to the JIT that unused is unreachable
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    GcFinalization.awaitDone(future);
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    assertTrue(future.isDone());
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    assertTrue(future.isCancelled());
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  }
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  public void testAwaitClear() {
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    final WeakReference<Object> ref = new WeakReference<>(new Object());
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    GcFinalization.awaitClear(ref);
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    assertNull(ref.get());
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  }
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  public void testAwaitDone_finalizationPredicate() {
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    final WeakHashMap<Object, Object> map = new WeakHashMap<>();
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    map.put(new Object(), Boolean.TRUE);
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    GcFinalization.awaitDone(
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        new FinalizationPredicate() {
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          @Override
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          public boolean isDone() {
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            return map.isEmpty();
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          }
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        });
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    assertTrue(map.isEmpty());
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  }
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  // ----------------------------------------------------------------
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  // Test that interrupts result in RuntimeException, not InterruptedException.
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  // Trickier than it looks, because runFinalization swallows interrupts.
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  // ----------------------------------------------------------------
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  class Interruptenator extends Thread {
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    final AtomicBoolean shutdown;
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    Interruptenator(final Thread interruptee) {
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      this(interruptee, new AtomicBoolean(false));
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    }
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    Interruptenator(final Thread interruptee, final AtomicBoolean shutdown) {
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      super(
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          new Runnable() {
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            @Override
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            public void run() {
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              while (!shutdown.get()) {
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                interruptee.interrupt();
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                Thread.yield();
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              }
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            }
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          });
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      this.shutdown = shutdown;
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      start();
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    }
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    void shutdown() {
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      shutdown.set(true);
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      while (this.isAlive()) {
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        Thread.yield();
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      }
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    }
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  }
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  void assertWrapsInterruptedException(RuntimeException e) {
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    assertThat(e).hasMessageThat().contains("Unexpected interrupt");
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    assertThat(e).hasCauseThat().isInstanceOf(InterruptedException.class);
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  }
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  public void testAwait_countDownLatch_interrupted() {
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    Interruptenator interruptenator = new Interruptenator(Thread.currentThread());
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    try {
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      final CountDownLatch latch = new CountDownLatch(1);
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      RuntimeException expected =
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          assertThrows(RuntimeException.class, () -> GcFinalization.await(latch));
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      assertWrapsInterruptedException(expected);
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    } finally {
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      interruptenator.shutdown();
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      Thread.interrupted();
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    }
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  }
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  public void testAwaitDone_future_interrupted_interrupted() {
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    Interruptenator interruptenator = new Interruptenator(Thread.currentThread());
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    try {
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      final SettableFuture<@Nullable Void> future = SettableFuture.create();
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      RuntimeException expected =
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          assertThrows(RuntimeException.class, () -> GcFinalization.awaitDone(future));
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      assertWrapsInterruptedException(expected);
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    } finally {
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      interruptenator.shutdown();
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      Thread.interrupted();
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    }
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  }
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  public void testAwaitClear_interrupted() {
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    Interruptenator interruptenator = new Interruptenator(Thread.currentThread());
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    try {
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      final WeakReference<Object> ref = new WeakReference<Object>(Boolean.TRUE);
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      RuntimeException expected =
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          assertThrows(RuntimeException.class, () -> GcFinalization.awaitClear(ref));
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      assertWrapsInterruptedException(expected);
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    } finally {
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      interruptenator.shutdown();
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      Thread.interrupted();
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    }
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  }
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  public void testAwaitDone_finalizationPredicate_interrupted() {
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    Interruptenator interruptenator = new Interruptenator(Thread.currentThread());
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    try {
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      RuntimeException expected =
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          assertThrows(
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              RuntimeException.class,
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              () ->
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                  GcFinalization.awaitDone(
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                      new FinalizationPredicate() {
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                        @Override
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                        public boolean isDone() {
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                          return false;
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                        }
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                      }));
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      assertWrapsInterruptedException(expected);
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    } finally {
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      interruptenator.shutdown();
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      Thread.interrupted();
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    }
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  }
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  /**
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   * awaitFullGc() is not quite as reliable a way to ensure calling of a specific finalize method as
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   * the more direct await* methods, but should be reliable enough in practice to avoid flakiness of
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   * this test. (And if it isn't, we'd like to know about it first!)
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   */
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  public void testAwaitFullGc() {
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    final CountDownLatch finalizerRan = new CountDownLatch(1);
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    final WeakReference<Object> ref =
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        new WeakReference<Object>(
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            new Object() {
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              @SuppressWarnings({"removal", "Finalize"}) // b/260137033
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              @Override
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              protected void finalize() {
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                finalizerRan.countDown();
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              }
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            });
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    // Don't copy this into your own test!
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    // Use e.g. awaitClear or await(CountDownLatch) instead.
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    GcFinalization.awaitFullGc();
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    // If this test turns out to be flaky, add a second call to awaitFullGc()
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    // GcFinalization.awaitFullGc();
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    assertEquals(0, finalizerRan.getCount());
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    assertNull(ref.get());
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  }
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}
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