* the given {@code comparator}.
   *
   * @see #testComparator(Comparator, List)
   */
  public static <T extends @Nullable Object> void testComparator(
      Comparator<? super T> comparator, T... valuesInExpectedOrder) {
    testComparator(comparator, asList(valuesInExpectedOrder));
  }

  /**

   * the given {@code comparator}.
   *
   * @see #testComparator(Comparator, List)
   */
  public static <T extends @Nullable Object> void testComparator(
      Comparator<? super T> comparator, T... valuesInExpectedOrder) {
    testComparator(comparator, asList(valuesInExpectedOrder));
  }

  /**

    // Now we don't care what order it's put the list in, only that
    // comparing any pair of elements gives the answer we expect.
    testComparator(arbitrary, list);
  }

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

    // Now we don't care what order it's put the list in, only that
    // comparing any pair of elements gives the answer we expect.
    testComparator(arbitrary, list);
  }

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

import static com.google.common.collect.testing.Helpers.assertEmpty;
import static com.google.common.collect.testing.Helpers.assertEqualInOrder;
import static com.google.common.collect.testing.Helpers.testComparator;
import static java.util.Arrays.asList;
import static java.util.Collections.emptyIterator;
import static java.util.Collections.singleton;
import static org.junit.Assert.assertThrows;

import static com.google.common.collect.testing.Helpers.assertEmpty;
import static com.google.common.collect.testing.Helpers.assertEqualInOrder;
import static com.google.common.collect.testing.Helpers.testComparator;
import static java.util.Arrays.asList;
import static java.util.Collections.emptyIterator;
import static java.util.Collections.singleton;
import static org.junit.Assert.assertThrows;

                MapFeature.ALLOWS_NULL_VALUES,
                CollectionFeature.SUPPORTS_ITERATOR_REMOVE)
            .createTestSuite());

    return suite;
  }

  public void testComparator() {
    assertThat(create().comparator()).isNotNull();
  }

  public void testCeilingEntry() {
    assertThat(create().ceilingEntry("a")).isNull();
  }

  public void testCeilingKey() {

    TreeMultimap<@Nullable String, @Nullable Integer> multimap = createPopulate();
    assertThat(multimap.values()).containsExactly(7, 3, 1, null, 0, 6, 2).inOrder();
  }

  public void testComparator() {
    TreeMultimap<@Nullable String, @Nullable Integer> multimap = createPopulate();
    assertEquals(DECREASING_INT_COMPARATOR, multimap.get("foo").comparator());

    Comparator<byte[]> comparator = UnsignedBytes.lexicographicalComparator();
    Helpers.testComparator(comparator, ordered);
    assertThat(SerializableTester.reserialize(comparator)).isSameInstanceAs(comparator);

    // The Java implementation.
    Comparator<byte[]> javaImpl = UnsignedBytes.lexicographicalComparatorJavaImpl();
    Helpers.testComparator(javaImpl, ordered);

    Comparator<byte[]> comparator = UnsignedBytes.lexicographicalComparator();
    Helpers.testComparator(comparator, ordered);
    assertThat(SerializableTester.reserialize(comparator)).isSameInstanceAs(comparator);

    // The Java implementation.
    Comparator<byte[]> javaImpl = UnsignedBytes.lexicographicalComparatorJavaImpl();
    Helpers.testComparator(javaImpl, ordered);