@Override
    public boolean offer(E o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.offer(o);
    }

    @Override
    public @Nullable E poll() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.poll();
    }

    @Override
    public E remove() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.remove();
    }

    @Override

    BiMap<V, K> inv = getMap().inverse();
    getMap().clear();
    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeySetClearClearsInverse() {
    BiMap<V, K> inv = getMap().inverse();
    getMap().keySet().clear();
    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)

    }

    @Override
    public int size() {
      assertTrue(Thread.holdsLock(mutex));
      return super.size();
    }

    @Override
    public boolean isEmpty() {
      assertTrue(Thread.holdsLock(mutex));
      return super.isEmpty();
    }

    @Override
    public @Nullable V remove(Object object) {
      assertTrue(Thread.holdsLock(mutex));
      return super.remove(object);
    }

                        assertTrue(executor.isShutdown());
                        assertFalse(executor.isTerminated());

                        // WAIT #3
                        barrier.await(1, SECONDS);
                        return null;
                      });
              assertTrue(future.isDone());
              assertTrue(executor.isShutdown());

    assertTrue(inner.isCancelled());
    assertTrue(inner.wasInterrupted());
    assertThrows(CancellationException.class, () -> inner.get());
  }

  public void testCancel_resultCancelsInner() throws Exception {
    SettableFuture<Object> async = SettableFuture.create();
    SettableFuture<Object> inner = SettableFuture.create();
    async.setFuture(inner);
    async.cancel(false);
    assertTrue(inner.isCancelled());

    assertTrue(latch.await(5, SECONDS));
    assertTrue(future.isDone());
    assertTrue(future.isCancelled());

    assertThrows(CancellationException.class, () -> future.get());
  }

  public void testFailedFuture(@Nullable String message) throws InterruptedException {
    assertTrue(future.isDone());
    assertFalse(future.isCancelled());

    assertTrue(latch.await(5, SECONDS));
    assertTrue(future.isDone());

        // Digits are greater than letters
        assertTrue(seven.compareTo(capitalJ) > 0, "expected 7 > J");
        assertTrue(capitalJ.compareTo(seven) < 0, "expected J < 1");
        assertTrue(seven.compareTo(lowerCaseC) > 0, "expected 7 > c");
        assertTrue(lowerCaseC.compareTo(seven) < 0, "expected c < 7");
    }

    @Test
    void testNonAsciiDigits() { // These should not be treated as digits.

    assertThat(e).hasCauseThat().isInstanceOf(IllegalStateException.class);

    assertTrue(listenerLatch.await(5, SECONDS));
    assertTrue(task.isDone());
    assertFalse(task.isCancelled());
  }

  public void testListenerCalledOnCancelFromNotRunning() throws Exception {
    task.cancel(false);
    assertTrue(task.isDone());
    assertTrue(task.isCancelled());
    assertEquals(1, runLatch.getCount());

    assertTrue(TypeToken.of(char[][].class).isArray());
    assertTrue(TypeToken.of(byte[].class).isArray());
    assertTrue(TypeToken.of(short[].class).isArray());
    assertTrue(TypeToken.of(int[].class).isArray());
    assertTrue(TypeToken.of(long[].class).isArray());
    assertTrue(TypeToken.of(float[].class).isArray());
    assertTrue(TypeToken.of(double[].class).isArray());

    Collection<V> result = multimap().get(k0());
    assertTrue(result.add(v3()));
    assertTrue(multimap().containsKey(k0()));
    assertEquals(getNumElements() + 1, multimap().size());
    assertTrue(multimap().containsEntry(k0(), v3()));
  }

  @MapFeature.Require(SUPPORTS_PUT)
  public void testPropagatesAddAllToMultimap() {
    Collection<V> result = multimap().get(k0());
    assertTrue(result.addAll(singletonList(v3())));