assertEquals(maxMid, messageBlock.getMid());

        // Test with MIN_VALUE
        long minMid = Long.MIN_VALUE;
        doNothing().when(messageBlock).setMid(minMid);
        when(messageBlock.getMid()).thenReturn(minMid);

        messageBlock.setMid(minMid);
        assertEquals(minMid, messageBlock.getMid());

        // Test with zero
        long zeroMid = 0L;