### Question:
Relation { public People removePeople(People p) { People people = peoples.remove(p.getUsername()); synchronized ( changedFlag ) { changedFlag.add(p.username); } return people; }  UserId get_id(); void set_id(UserId _id); RelationType getType(); void setType(RelationType type); People removePeople(People p); void addPeople(People p); void modifyPeople(People p); People findPeopleByUserName(String name); Collection<People> listPeople(); User getParentUser(); void setParentUser(User parentUser); Set<String> clearChangeMark(); String toString(); Collection<FriendInfoLite> toBseFriendList(); static final int MAX_RELATION; }### Answer:
@Test public void testRemovePeople() { Relation relation = makeRelation(3); ArrayList<People> list = convertToList(relation.listPeople()); assertEquals(3, list.size()); relation.clearChangeMark(); relation.removePeople(makePeople("test-1")); Set<String> flags = relation.clearChangeMark(); assertEquals(1, flags.size()); assertEquals("test-1", flags.iterator().next()); assertEquals(0, relation.clearChangeMark().size()); }