How i am must test this method with mockito?

Method in service class:

@Override
@Transactional(readOnly = true)
public Collection<Account> searchAccounts(String partOfName) {
    Collection<Account> accounts = accountDao.getAll();
    CollectionUtils.filter(accounts, account ->
            account.getName().toLowerCase().contains(partOfName.toLowerCase()) ||
                    account.getSurname().toLowerCase().equalsIgnoreCase(partOfName.toLowerCase()));
    return accounts;
}

I am not understand what i must do with CollectionUtils.filter. mock this too? Now i have this in test class:

@Test
public void searchAccountsByPartOfName() throws ParseException {
    service.searchAccounts("test");
    verify(accountDao, times(1)).getAll();
}