* message must mention two values that were associated with the duplicate key in two different
   * calls to Builder.put (though we don't really care *which* two values if there were more than
   * two). These considerations lead us to have a field of type DuplicateKey in the Builder, which
   * will remember the first duplicate key we encountered. All later calls to buildOrThrow() can

                            "b", (Collection<String>) ImmutableSortedSet.of("bob", "bagel")),
                        Helpers.mapEntry(
                            "c", (Collection<String>) ImmutableSortedSet.of("carl", "carol")),
                        Helpers.mapEntry(
                            "d", (Collection<String>) ImmutableSortedSet.of("david", "dead")),
                        Helpers.mapEntry(

    for (int i = 0; i < 50; i++) {
      list.add(new Object());
    }

    Ordering<Object> arbitrary = Ordering.arbitrary();
    Collections.sort(list, arbitrary);

    // 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.
    Helpers.testComparator(arbitrary, list);

    assertEquals("Ordering.arbitrary()", arbitrary.toString());

    for (int i = 0; i < 50; i++) {
      list.add(new Object());
    }

    Ordering<Object> arbitrary = Ordering.arbitrary();
    Collections.sort(list, arbitrary);

    // 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.
    Helpers.testComparator(arbitrary, list);

    assertEquals("Ordering.arbitrary()", arbitrary.toString());

                            "b", (Collection<String>) ImmutableSortedSet.of("bob", "bagel")),
                        Helpers.mapEntry(
                            "c", (Collection<String>) ImmutableSortedSet.of("carl", "carol")),
                        Helpers.mapEntry(
                            "d", (Collection<String>) ImmutableSortedSet.of("david", "dead")),
                        Helpers.mapEntry(

   *       terminate whichever thread happens to trigger the execution.
   * </ul>
   *
   * A specific warning about locking: Code that executes user-supplied tasks, such as {@code
   * ListenableFuture} listeners, should take care not to do so while holding a lock. Additionally,
   * as a further line of defense, prefer not to perform any locking inside a task that will be run

              <!-- FeatureUtilTest.*ExampleDerivedInterfaceTester, com.google.common.io.*Tester, incidentally FeatureSpecificTestSuiteBuilderTest.MyAbstractTester (but we don't care either way because it's not meant to run on its own but works OK if it does)... but not NullPointerTesterTest, etc. -->
              <exclude>%regex[.*Tester.class]</exclude>

    try {
      builder.buildOrThrow();
      fail("Expected exception from duplicate keys");
    } catch (IllegalArgumentException expected) {
      // We don't really care which values the exception message contains, but they should be
      // different from each other. If buildKeepingLast() collapsed duplicates, that might end up
      // not being true.

  /**
   * Determines whether an edge has already been used during traversal. In the directed case a cycle
   * is always detected before reusing an edge, so no special logic is required. In the undirected
   * case, we must take care not to "backtrack" over an edge (i.e. going from A to B and then going
   * from B to A).
   */
  private static boolean canTraverseWithoutReusingEdge(