@Override public SlotAssignmentResult ensure(long key) {
        return super.ensure0(key, 0);
    }
@Test
    public void testPut() {
        final long key = random.nextLong();
        SlotAssignmentResult slot = insert(key);
        final long valueAddress = slot.address();
        assertTrue(slot.isNew());

        slot = hsa.ensure(key);
        assertFalse(slot.isNew());
        assertEquals(valueAddress, slot.address());
    }