### Question:
SimpleUserSystemService implements UserSystemService { public List<Group> findAllGroups() { return userGroupInfo.getGroups(); } SimpleUserSystemService(); @Override void start(); @Override String getName(); @Override List<User> findAllUsers(); List<Group> findAllGroups(); @Override void test(); @Override User findUser(String id); static final String USERS_FILE; static final String SKILLS_FILE; static final String AFFINITIES_FILE; static final String NAME; }### Answer:
@Test public void findAllGroups() { userSystem.start(); List<String> groupIds = userSystem.findAllGroups().stream() .map(Group::getId) .collect(Collectors.toList()); for (String user : GROUPS) { assertTrue("Group: " + user + " was not found", groupIds.contains(user)); } }