*     class under test.
   */
  protected abstract Map<K, V> makePopulatedMap() throws UnsupportedOperationException;

  /**
   * Creates a new key that is not expected to be found in {@link #makePopulatedMap()}.
   *
   * @return a key.
   * @throws UnsupportedOperationException if it's not possible to make a key that will not be found
   *     in the map.

  protected abstract SortedMap<K, V> makeEmptyMap() throws UnsupportedOperationException;

  @Override
  protected abstract SortedMap<K, V> makePopulatedMap() throws UnsupportedOperationException;

  @Override
  protected SortedMap<K, V> makeEitherMap() {
    try {
      return makePopulatedMap();
    } catch (UnsupportedOperationException e) {
      return makeEmptyMap();
    }
  }

  public void testTailMapWriteThrough() {

  protected abstract SortedMap<K, V> makeEmptyMap() throws UnsupportedOperationException;

  @Override
  protected abstract SortedMap<K, V> makePopulatedMap() throws UnsupportedOperationException;

  @Override
  protected SortedMap<K, V> makeEitherMap() {
    try {
      return makePopulatedMap();
    } catch (UnsupportedOperationException e) {
      return makeEmptyMap();
    }
  }

  public void testTailMapWriteThrough() {

    @Override
    protected Map<String, Integer> makeEmptyMap() {
      return makeTable().row('a');
    }

    @Override
    protected Map<String, Integer> makePopulatedMap() {
      Table<Character, String, Integer> table = makeTable();
      table.put('a', "one", 1);
      table.put('a', "two", 2);
      table.put('a', "three", 3);
      table.put('b', "four", 4);

@GwtCompatible
@NullUnmarked
public class ImmutableSortedMapSubMapMapInterfaceTest
    extends AbstractImmutableSortedMapMapInterfaceTest<String, Integer> {
  @Override
  protected SortedMap<String, Integer> makePopulatedMap() {
    return ImmutableSortedMap.of("a", 1, "b", 2, "c", 3, "d", 4, "e", 5).subMap("b", "d");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "a";
  }

  @Override

@GwtCompatible
@NullUnmarked
public class ImmutableSortedMapTailMapMapInterfaceTest
    extends AbstractImmutableSortedMapMapInterfaceTest<String, Integer> {
  @Override
  protected SortedMap<String, Integer> makePopulatedMap() {
    return ImmutableSortedMap.of("a", 1, "b", 2, "c", 3, "d", 4, "e", 5).tailMap("b");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "a";
  }

  @Override

@GwtCompatible
@NullUnmarked
public class ImmutableSortedMapTailMapMapInterfaceTest
    extends AbstractImmutableSortedMapMapInterfaceTest<String, Integer> {
  @Override
  protected SortedMap<String, Integer> makePopulatedMap() {
    return ImmutableSortedMap.of("a", 1, "b", 2, "c", 3, "d", 4, "e", 5).tailMap("b");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "a";
  }

  @Override

  @Override
  protected Map<Object, Integer> makeEmptyMap() {
    throw new UnsupportedOperationException();
  }

  @Override
  protected Map<Object, Integer> makePopulatedMap() {
    Colliders colliders = new Colliders();
    return ImmutableMap.of(
        colliders.e0(), 0,
        colliders.e1(), 1,
        colliders.e2(), 2,
        colliders.e3(), 3);
  }

  @Override

  @Override
  protected Map<String, String> makeEmptyMap() {
    return transformValues(new HashMap<String, String>(), Functions.<String>identity());
  }

  @Override
  protected Map<String, String> makePopulatedMap() {
    Map<String, Integer> underlying = new HashMap<>();
    underlying.put("a", 1);
    underlying.put("b", 2);
    underlying.put("c", 3);
    return transformValues(underlying, Functions.toStringFunction());
  }

    RowSortedTable<Character, String, Integer> table = TreeBasedTable.create();
    return unmodifiableRowSortedTable(table);
  }

  @Override
  protected Map<String, Integer> makePopulatedMap() {
    RowSortedTable<Character, String, Integer> table = TreeBasedTable.create();
    table.put('a', "one", 1);
    table.put('a', "two", 2);
    table.put('a', "three", 3);
    table.put('b', "four", 4);