protected <K, V> Map<K, V> create() {
    TestMap<K, V> inner = new TestMap<>(new HashMap<K, V>(), mutex);
    Map<K, V> outer = Synchronized.map(inner, mutex);
    return outer;
  }

  static class TestMap<K, V> extends ForwardingMap<K, V> implements Serializable {
    public final Object mutex;
    private final Map<K, V> delegate;

    public TestMap(Map<K, V> delegate, Object mutex) {
      checkNotNull(mutex);

import junit.framework.TestCase;
import org.jspecify.annotations.NullMarked;

/** Tests for {@code CollectSpliterators}. */
@GwtCompatible
@NullMarked
public class CollectSpliteratorsTest extends TestCase {
  public void testMap() {
    SpliteratorTester.of(
            () ->
                CollectSpliterators.map(
                    Arrays.spliterator(new String[] {"a", "b", "c", "d", "e"}), Ascii::toUpperCase))

        assertThat(hoge.getElementClassOfCollection(), is(sameClass(String.class)));
    }

    /**
     * @throws Exception
     */
    @Test
    public void testMap() throws Exception {
        final BeanDesc beanDesc = new BeanDescImpl(MyBean.class);
        final FieldDesc hoge = beanDesc.getFieldDesc("map");
        assertThat(hoge.getKeyClassOfMap(), is(sameClass(String.class)));