How to Unit Test AggregateIterable<User> - mongodb

Question

Struggling to Mock what to return when using AggregateIterable in Java/Mongo.
I have tried using MongoCursor but struggling to understand this. I want to cover all paths with Unit Tests for this. What are the best possible ways using mockito and testNG.
public List<User> getAggregatedList(User user){
AggregateIterable<User> agg = collection.aggregate(pipeline, User.class)
List<User> users = new ArrayList<>();
if (agg != null){
Iterator<User> it = agg.iterator();
while(it.hasNext()){
users.add(it.next());
}
}
return users;
}
I should be able to write a test such as:
...
expected = Arrays.asList(user1,user2...)
verify(result,expect)

Answer 1

You can test it by mocking the hasNext() and next() methods of the iterator like so:
#Test
public void testGetAggregatedList() {
MongoCollection collection = PowerMockito.mock(MongoCollection.class);
AggregateIterable<User> iterable = PowerMockito.mock(AggregateIterable.class);
MongoClient client = PowerMockito.mock(MongoClient.class);
MongoDatabase db = PowerMockito.mock(MongoDatabase.class);
MongoCursor iterator = PowerMockito.mock(MongoCursor.class);
User user1 = PowerMockito.mock(User.class);
User user2 = PowerMockito.mock(User.class);
MongoDaoDelegator.setClient(client);
PowerMockito.when(client.getDatabase(anyString())).thenReturn(db);
PowerMockito.when(db.getCollection(anyString())).thenReturn(collection);
PowerMockito.when(collection.aggregate(anyList(),any())).thenReturn(iterable);
PowerMockito.when(iterable.iterator()).thenReturn(iterator);
PowerMockito.when(iterator.hasNext()).thenReturn(true,true,false);
PowerMockito.when(iterator.next()).thenReturn(user1,user2);
getAggregatedList(new User());
}
This will give you the result you are expecting.