@Override public SlotAssignmentResult ensure(long key1, long key2) {
        assert key1 != unassignedSentinel : "ensure() called with key1 == nullKey1 (" + unassignedSentinel + ')';
        return super.ensure0(key1, key2);
    }
@Test
    public void testCursor_key1() {
        final long key1 = randomKey();
        final long key2 = randomKey();
        hsa.ensure(key1, key2);

        HashSlotCursor16byteKey cursor = hsa.cursor();
        cursor.advance();
        assertEquals(key1, cursor.key1());
    }