@Override
    public boolean confirm(String key) {
        return cache.asMap().containsKey(key);
    }
@Test
    void testConfirm() {
        // add first key and confirm
        assertTrue(repo.add(key01));
        assertTrue(repo.confirm(key01));

        // try to confirm a key that isn't there
        assertFalse(repo.confirm(key02));
    }