assertSame(
        ImmutableClassToInstanceMap.of(),
        SerializableTester.reserialize(ImmutableClassToInstanceMap.of()));
  }

  public void testCopyOf_map_empty() {
    Map<Class<?>, Object> in = emptyMap();
    ClassToInstanceMap<Object> map = ImmutableClassToInstanceMap.copyOf(in);
    assertTrue(map.isEmpty());
    assertSame(map, ImmutableClassToInstanceMap.of());

 * and a primitive type and its corresponding wrapper type may map to different values.
 *
 * <h3>Implementations</h3>
 *
 * <ul>
 *   <li>{@link ImmutableClassToInstanceMap}
 *   <li>{@link MutableClassToInstanceMap}
 * </ul>
 *
 * <p>To map a generic type to an instance of that type, use {@link
 * com.google.common.reflect.TypeToInstanceMap} instead.
 *

import java.util.Set;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * A mutable class-to-instance map backed by an arbitrary user-provided map. See also {@link
 * ImmutableClassToInstanceMap}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#classtoinstancemap">{@code
 * ClassToInstanceMap}</a>.
 *
 * @author Kevin Bourrillion