@Override
    @ManagedOperation(description = "Adds the key to the store")
    public boolean add(String key) {
        if (cache.asMap().containsKey(key)) {
            return false;
        } else {
            cache.put(key, true);
            return true;
        }
    }
@Test
    void testAdd() {
        // add first key
        assertTrue(repo.add(key01));
        assertTrue(repo.getCache().asMap().containsKey(key01));

        // try to add the same key again
        assertFalse(repo.add(key01));

        // try to add another one
        assertTrue(repo.add(key02));
        assertTrue(repo.getCache().asMap().containsKey(key02));
    }