val headers =
      Headers
        .Builder()
        .add("content-length", "99")
        .add("authorization", "peanutbutter")
        .add("proxy-authorization", "chocolate")
        .add("cookie", "drink=coffee")
        .add("set-cookie", "accessory=sugar")
        .add("user-agent", "OkHttp")
        .build()
    assertThat(headers.toString()).isEqualTo(
      """
      |content-length: 99
      |authorization: ██

  public void testOffer_supportedNotPresent() {
    assertTrue("offer(notPresent) should return true", getQueue().offer(e3()));
    expectAdded(e3());
  }

  @CollectionFeature.Require({SUPPORTS_ADD, ALLOWS_NULL_VALUES})
  public void testOffer_nullSupported() {
    assertTrue("offer(null) should return true", getQueue().offer(null));
    expectAdded((E) null);
  }

  public void testOffer_supportedNotPresent() {
    assertTrue("offer(notPresent) should return true", getQueue().offer(e3()));
    expectAdded(e3());
  }

  @CollectionFeature.Require({SUPPORTS_ADD, ALLOWS_NULL_VALUES})
  public void testOffer_nullSupported() {
    assertTrue("offer(null) should return true", getQueue().offer(null));
    expectAdded((E) null);
  }

 * to the methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change
 * the behaviour of {@link #offer} which can lead to unexpected behaviour. In this case, you should
 * override {@code offer} as well, either providing your own implementation, or delegating to the
 * provided {@code standardOffer} method.
 *

 * to the methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change
 * the behaviour of {@link #offer} which can lead to unexpected behaviour. In this case, you should
 * override {@code offer} as well, either providing your own implementation, or delegating to the
 * provided {@code standardOffer} method.
 *

    return delegate().drainTo(c);
  }

  @CanIgnoreReturnValue // TODO(kak): consider removing this
  @Override
  public boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException {
    return delegate().offer(e, timeout, unit);
  }

  @CanIgnoreReturnValue // TODO(kak): consider removing this
  @Override

 * to the methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change
 * the behaviour of {@link #offer} which can lead to unexpected behaviour. In this case, you should
 * override {@code offer} as well, either providing your own implementation, or delegating to the
 * provided {@code standardOffer} method.
 *

 * methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change the
 * behavior of {@link #offer} which can lead to unexpected behavior. In this case, you should
 * override {@code offer} as well.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code

    private final Deque<E> delegate = new LinkedList<>();
    private final Object mutex = new Object[0]; // something Serializable

    @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

    return delegate().drainTo(c);
  }

  @CanIgnoreReturnValue // TODO(kak): consider removing this
  @Override
  public boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException {
    return delegate().offer(e, timeout, unit);
  }

  @CanIgnoreReturnValue // TODO(kak): consider removing this
  @Override