when(backingMap.putIfAbsent(eq(KEY), isA(AtomicInteger.class))).thenReturn(existingZero);
    // since the putIfAbsent returned a zero, we'll try to replace...
    when(backingMap.replace(eq(KEY), eq(existingZero), isA(AtomicInteger.class))).thenReturn(false);
    // ...and then putIfAbsent. Simulate failure on both
    when(backingMap.putIfAbsent(eq(KEY), isA(AtomicInteger.class))).thenReturn(existing);

        assertFalse(it.hasNext());

        // Verify interactions
        verify(tree, times(1)).send(isA(Trans2FindFirst2.class), any(Trans2FindFirst2Response.class));
        // Verify that Trans2FindNext2 was sent twice for fetching more entries
        verify(tree, times(2)).send(isA(Trans2FindNext2.class), any(Trans2FindFirst2Response.class));

        // Close should have sent FindClose2 exactly once

        h.release();
        verify(tree, never()).send(isA(Smb2CloseRequest.class), any());
        verify(tree, never()).send(any(CommonServerMessageBlockRequest.class), any(SmbComBlankResponse.class), any(RequestParam[].class));

        // Second release: should close now via SMB2 path
        h.release();
        verify(tree, times(1)).send(isA(Smb2CloseRequest.class), eq(RequestParam.NO_RETRY));