// user-specified -XX:+DisableExplicitGC.
    //
    // TODO(user): Consider using
    // java/lang/management/OperatingSystemMXBean.html#getSystemLoadAverage()
    //
    // TODO(user): Consider scaling by number of mutator threads,
    // e.g. using Thread#activeCount()
    return max(10L, Runtime.getRuntime().totalMemory() / (32L * 1024L * 1024L));
  }

  /**

    // user-specified -XX:+DisableExplicitGC.
    //
    // TODO(user): Consider using
    // java/lang/management/OperatingSystemMXBean.html#getSystemLoadAverage()
    //
    // TODO(user): Consider scaling by number of mutator threads,
    // e.g. using Thread#activeCount()
    return max(10L, Runtime.getRuntime().totalMemory() / (32L * 1024L * 1024L));
  }

  /**

   *
   * <p>A collection is considered immutable if:
   *
   * <ol>
   *   <li>All its mutation methods result in UnsupportedOperationException, and do not change the
   *       underlying contents.
   *   <li>All methods that return objects that can indirectly mutate the collection throw
   *       UnsupportedOperationException when those mutators are called.
   * </ol>
   *
   * @param collection the presumed-immutable collection

   *
   * <p>A collection is considered immutable if:
   *
   * <ol>
   *   <li>All its mutation methods result in UnsupportedOperationException, and do not change the
   *       underlying contents.
   *   <li>All methods that return objects that can indirectly mutate the collection throw
   *       UnsupportedOperationException when those mutators are called.
   * </ol>
   *
   * @param collection the presumed-immutable collection

     * existing values in the execution request that are controlled by the toolchains. Hence, it is expected that this
     * method is called on a new/empty execution request before the caller mutates it to fit its needs.
     *
     * @param request The execution request to populate, must not be {@code null}.
     * @param toolchains The toolchains to copy into the execution request, may be {@code null}.

    assertSideEffectFree(hash);
    assertReadableBytes(hash);
  }

  private static void assertSideEffectFree(HashCode hash) {
    byte[] original = hash.asBytes();
    byte[] mutated = hash.asBytes();
    mutated[0]++;
    assertTrue(Arrays.equals(original, hash.asBytes()));
  }

  private static void assertReadableBytes(HashCode hashCode) {
    assertTrue(hashCode.bits() >= 32); // sanity

      <T extends @Nullable Object> Scenario<?> mutate(Scenario<T> scenario) {
        List<T> newList = Lists.newArrayList(scenario.strictlyOrderedList);
        Collections.reverse(newList);
        return new Scenario<T>(scenario.ordering.reverse(), newList, scenario.emptyArray);
      }
    },
    NULLS_FIRST {
      @Override
      <T extends @Nullable Object> Scenario<?> mutate(Scenario<T> scenario) {

      <T extends @Nullable Object> Scenario<?> mutate(Scenario<T> scenario) {
        List<T> newList = Lists.newArrayList(scenario.strictlyOrderedList);
        Collections.reverse(newList);
        return new Scenario<T>(scenario.ordering.reverse(), newList, scenario.emptyArray);
      }
    },
    NULLS_FIRST {
      @Override
      <T extends @Nullable Object> Scenario<?> mutate(Scenario<T> scenario) {

    assertSideEffectFree(hash);
    assertReadableBytes(hash);
  }

  private static void assertSideEffectFree(HashCode hash) {
    byte[] original = hash.asBytes();
    byte[] mutated = hash.asBytes();
    mutated[0]++;
    assertTrue(Arrays.equals(original, hash.asBytes()));
  }

  private static void assertReadableBytes(HashCode hashCode) {
    assertTrue(hashCode.bits() >= 32); // sanity

 *   ...
 * }
 * </pre>
 *
 * <p>No cascading checks are performed against the return values of methods unless the method is a
 * static factory method. Neither are semantics of mutation methods such as {@code
 * someList.add(obj)} checked. For more detailed discussion of supported and unsupported cases, see
 * {@link #testEquals}, {@link #testNulls} and {@link #testSerializable}.
 *