testComparator(arbitrary, list);
  }

  public void testUsingToString() {
    Ordering<Object> ordering = Ordering.usingToString();
    testComparator(ordering, 1, 12, 124, 2);
    assertThat(ordering.toString()).isEqualTo("Ordering.usingToString()");
    assertThat(reserialize(ordering)).isSameInstanceAs(ordering);
  }

  // use an enum to get easy serializability

    testComparator(arbitrary, list);
  }

  public void testUsingToString() {
    Ordering<Object> ordering = Ordering.usingToString();
    testComparator(ordering, 1, 12, 124, 2);
    assertThat(ordering.toString()).isEqualTo("Ordering.usingToString()");
    assertThat(reserialize(ordering)).isSameInstanceAs(ordering);
  }

  // use an enum to get easy serializability

    Ordering<@Nullable Comparable<?>> result = nullsLast;
    if (result == null) {
      result = nullsLast = super.<Comparable<?>>nullsLast();
    }
    return (Ordering<@Nullable S>) result;
  }

  @Override
  @SuppressWarnings("unchecked") // TODO(kevinb): the right way to explain this??
  public <S extends Comparable<?>> Ordering<S> reverse() {

    Ordering<@Nullable Comparable<?>> result = nullsLast;
    if (result == null) {
      result = nullsLast = super.<Comparable<?>>nullsLast();
    }
    return (Ordering<@Nullable S>) result;
  }

  @Override
  @SuppressWarnings("unchecked") // TODO(kevinb): the right way to explain this??
  public <S extends Comparable<?>> Ordering<S> reverse() {

  /**
   * The type of ordering that this object specifies.
   *
   * <ul>
   *   <li>UNORDERED: no order is guaranteed.
   *   <li>STABLE: ordering is guaranteed to follow a pattern that won't change between releases.
   *       Some methods may have stronger guarantees.
   *   <li>INSERTION: insertion ordering is guaranteed.
   *   <li>SORTED: ordering according to a supplied comparator is guaranteed.
   * </ul>

import static com.google.common.truth.Truth.assertThat;

import com.google.common.collect.Ordering;
import java.util.Comparator;
import org.jspecify.annotations.NullUnmarked;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** Tests for ordering the elements of graphs. */
@RunWith(JUnit4.class)
@NullUnmarked
public final class ElementOrderTest {

 * {@link PriorityQueue} and supplies blocking retrieval operations. While this queue is logically
 * unbounded, attempted additions may fail due to resource exhaustion (causing {@code
 * OutOfMemoryError}). This class does not permit {@code null} elements. A priority queue relying on
 * {@linkplain Comparable natural ordering} also does not permit insertion of non-comparable objects

    lockA.lock();
  }

  // Tests transitive deadlock detection.
  public void testDeadlock_threeLocks() {
    // Establish an ordering from lockA -> lockB.
    lockA.lock();
    lockB.lock();
    lockB.unlock();
    lockA.unlock();

    // Establish an ordering from lockB -> lockC.
    lockB.lock();
    lockC.lock();
    lockB.unlock();

    // lockC -> lockA should fail.

    lockA.lock();
  }

  // Tests transitive deadlock detection.
  public void testDeadlock_threeLocks() {
    // Establish an ordering from lockA -> lockB.
    lockA.lock();
    lockB.lock();
    lockB.unlock();
    lockA.unlock();

    // Establish an ordering from lockB -> lockC.
    lockB.lock();
    lockC.lock();
    lockB.unlock();

    // lockC -> lockA should fail.

    assertEquals(tree, copyFromTree);
    assertThat(copyFromTree.keyComparator()).isEqualTo(Ordering.natural());
    assertThat(copyFromTree.valueComparator()).isEqualTo(Ordering.natural());
    assertThat(copyFromTree.get(1.0).comparator()).isEqualTo(Ordering.natural());
  }

  /** Test that creating one TreeMultimap from a non-TreeMultimap results in natural ordering. */
  public void testCreateFromHashMultimap() {