suite.addTest(
        NavigableMapTestSuiteBuilder.using(
                new TestStringSortedMapGenerator() {
                  @Override
                  protected NavigableMap<String, String> create(Entry<String, String>[] entries) {
                    NavigableMap<String, String> map = new SafeTreeMap<>();
                    putEntries(map, entries);
                    map.put("banana", "toast");

    }
  }

  private final class NavigableAsMap extends SortedAsMap implements NavigableMap<K, Collection<V>> {

    NavigableAsMap(NavigableMap<K, Collection<V>> submap) {
      super(submap);
    }

    @Override
    NavigableMap<K, Collection<V>> sortedMap() {
      return (NavigableMap<K, Collection<V>>) super.sortedMap();
    }

    @Override
    @CheckForNull

  }

  @GwtIncompatible // NavigableMap
  static <K extends @Nullable Object, V extends @Nullable Object> NavigableMap<K, V> navigableMap(
      NavigableMap<K, V> navigableMap) {
    return navigableMap(navigableMap, null);
  }

  @GwtIncompatible // NavigableMap
  static <K extends @Nullable Object, V extends @Nullable Object> NavigableMap<K, V> navigableMap(

  }

  @GwtIncompatible // NavigableMap
  static <K extends @Nullable Object, V extends @Nullable Object> NavigableMap<K, V> navigableMap(
      NavigableMap<K, V> navigableMap) {
    return navigableMap(navigableMap, null);
  }

  @GwtIncompatible // NavigableMap
  static <K extends @Nullable Object, V extends @Nullable Object> NavigableMap<K, V> navigableMap(

    return SortedMapTestSuiteBuilder.using(
            new TestStringSortedMapGenerator() {
              @Override
              protected NavigableMap<String, String> create(Entry<String, String>[] entries) {
                NavigableMap<String, String> map = populate(new TreeMap<String, String>(), entries);
                return Collections.checkedNavigableMap(map, String.class, String.class);
              }

    }
  }

  private final class NavigableAsMap extends SortedAsMap implements NavigableMap<K, Collection<V>> {

    NavigableAsMap(NavigableMap<K, Collection<V>> submap) {
      super(submap);
    }

    @Override
    NavigableMap<K, Collection<V>> sortedMap() {
      return (NavigableMap<K, Collection<V>>) super.sortedMap();
    }

    @Override
    @CheckForNull

import com.google.common.collect.testing.features.MapFeature;
import com.google.common.testing.SerializableTester;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NavigableMap;
import java.util.SortedMap;
import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;

/**
 * Tests for SafeTreeMap.
 *
 * @author Louis Wasserman
 */

import com.google.common.collect.testing.features.MapFeature;
import com.google.common.testing.SerializableTester;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NavigableMap;
import java.util.SortedMap;
import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;

/**
 * Tests for SafeTreeMap.
 *
 * @author Louis Wasserman
 */

    /*
     * We'd like to sanity check that we didn't get a NavigableMap out, but we
     * can't easily do so while maintaining GWT compatibility.
     */
    assertEquals(ImmutableSortedMap.of("a", 2.0, "b", 3.0), transformed);
  }

  @GwtIncompatible // NavigableMap
  public void testNavigableMapTransformValues() {
    NavigableMap<String, Integer> map = ImmutableSortedMap.of("a", 4, "b", 9);

   * NavigableMap}, instead of the {@link java.util.Map} specified in the {@link Multimap}
   * interface.
   *
   * @since 14.0 (present with return type {@code SortedMap} since 2.0)
   */
  @Override
  public NavigableMap<K, Collection<V>> asMap() {
    return (NavigableMap<K, Collection<V>>) super.asMap();
  }

  /**