doNothing().when(idempotentTree).close();

        // Close multiple times
        idempotentTree.close();
        idempotentTree.close();

        // Verify close was called, but implementation should handle idempotency
        verify(idempotentTree, times(2)).close();
    }

    /**
     * Test for unwrap with null parameter.
     * Verifies behavior when null is passed to unwrap.

 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *

        // Act: len==0 triggers initial token construction
        byte[] out = ctx.initSecContext(null, 0, 0);

        // Assert: returns a SPNEGO token (opaque here but non-null/non-empty)
        assertNotNull(out);
        assertTrue(out.length > 0);

        // Verify interactions: flags and an empty optimistic token are used
        verify(this.mechContext, times(1)).getFlags();

 * {@link #enqueue} and {@link #dispatch} are 2 different methods. It is expected that the decision
 * to run a particular event is made during the state change, but the decision to actually invoke
 * the listeners can be delayed slightly so that locks can be dropped. Also, because {@link
 * #dispatch} is expected to be called concurrently, it is idempotent.
 */
@J2ktIncompatible

 * @author Jens Nyman
 * @param <N> Node parameter type
 * @param <V> Value parameter type
 * @since 20.0
 */
@Beta
@Immutable(containerOf = {"N", "V"})
@SuppressWarnings("Immutable") // Extends StandardValueGraph but uses ImmutableMaps.
public final class ImmutableValueGraph<N, V> extends StandardValueGraph<N, V> {

  private ImmutableValueGraph(ValueGraph<N, V> graph) {

// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

   *       between paging memory and killing other processes - so allocating a gigantic buffer and
   *       then sequentially accessing it could result in other processes dying. This is solvable
   *       via madvise(2), but that obviously doesn't exist in java.
   *   <li>Ordinary copy. Kernel copies bytes into a kernel buffer, from a kernel buffer into a
   *       userspace buffer (byte[] or ByteBuffer), then copies them from that buffer into the

 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *

 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *