@Override public SlotAssignmentResult ensure(long key1, long key2) {
        return super.ensure0(key1, key2);
    }
@Test
    public void testPut() {
        final long key1 = randomKey();
        final long key2 = randomKey();
        SlotAssignmentResult slot = insert(key1, key2);
        assertTrue(slot.isNew());
        final long valueAddress = slot.address();

        slot = hsa.ensure(key1, key2);
        assertFalse(slot.isNew());
        assertEquals(valueAddress, slot.address());
    }