How to System Design Trade Position Aggregator? [Solution]

import org.junit.Ignore;
import java.util.Iterator;
import java.util.List;
import java.util.ArrayList;
import org.junit.Test;
import static org.junit.Assert.;

public class PositionManagerTest {
   
    public PositionManagerTest() {
    }
   
    @Ignore
    public void testGetRealTimePosition() {
        assertEquals(1, 1);
    }

    @Test
    public void testGetPositionForAccountAndSecurity() {
        PositionManager pMgr = new PositionManager();
        List<Trade> tradeStream = createTrades();
       
        Iterator<Trade> itr = tradeStream.iterator();
       
        while(itr.hasNext()) {
            pMgr.process(itr.next());
            itr.remove();
        }
       
        assertEquals(200, pMgr.getPositionForAccountAndSecurity("ACC-101", "MSFT"));
        assertEquals(150, pMgr.getPositionForAccountAndSecurity("ACC-102", "INFY"));
        assertEquals(250, pMgr.getPositionForAccountAndSecurity("ACC-103", "REP"));
        assertEquals(150, pMgr.getPositionForAccountAndSecurity("ACC-104", "HKJ"));
        assertEquals(200, pMgr.getPositionForAccountAndSecurity("ACC-105", "FVE"));
        assertEquals(50,  pMgr.getPositionForAccountAndSecurity("ACC-105", "AMZ"));
        assertEquals(150, pMgr.getPositionForAccountAndSecurity("ACC-106", "ABC"));
        assertEquals(-50, pMgr.getPositionForAccountAndSecurity("ACC-107", "META"));
        assertEquals(200, pMgr.getPositionForAccountAndSecurity("ACC-108", "OLA"));
        assertEquals(200, pMgr.getPositionForAccountAndSecurity("ACC-109", "BCD"));
        assertEquals(-200,pMgr.getPositionForAccountAndSecurity("ACC-110", "BCD"));
        assertEquals(100, pMgr.getPositionForAccountAndSecurity("ACC-111", "EFG"));
        assertEquals(0, pMgr.getPositionForAccountAndSecurity("ACC-112", "BES"));
        assertEquals(0, pMgr.getPositionForAccountAndSecurity("ACC-113", "KBC"));
       
        //validate the total number of trades
       
        //validate correct account contain correct trades
       
    }
   
 
    private List<Trade> createTrades(){
        List<Trade> trades = new ArrayList<Trade>();
       
        //simple increment
        trades.add(new Trade(5001,"ACC-101", 1, "MSFT", 100,
                Direction.BUY, Operation.NEW));
        trades.add(new Trade(5002,"ACC-101", 1, "MSFT", 100, 
                Direction.BUY, Operation.NEW));
               
        //simple increment for another security
        trades.add(new Trade(5003,"ACC-102", 1, "INFY", 50,  
                Direction.BUY, Operation.NEW));
        trades.add(new Trade(5004,"ACC-102", 1, "INFY", 100, 
                Direction.BUY, Operation.NEW));
       
        //simple  NEW - AMEND - NEW (quantity)
        trades.add(new Trade(5005,"ACC-103", 1, "REP", 100,  
            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5005,"ACC-103", 2, "REP", 50, 
            Direction.BUY, Operation.AMEND));
        trades.add(new Trade(5006,"ACC-103", 1, "REP", 200, 
            Direction.BUY, Operation.NEW));
       
        //simpel BUY SELL BUY Scenario
        trades.add(new Trade(5007, "ACC-104", 1, "HKJ", 100,  
            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5008, "ACC-104", 1, "HKJ", 50, 
            Direction.SELL, Operation.NEW));
        trades.add(new Trade(5009, "ACC-104", 1, "HKJ", 100, 
            Direction.BUY, Operation.NEW));
       
        //security amendment scenario
        trades.add(new Trade(5010, "ACC-105", 1, "FVE", 100,  
            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5010, "ACC-105", 2, "AMZ", 50, 
            Direction.BUY, Operation.AMEND));
        trades.add(new Trade(5011, "ACC-105", 1, "FVE", 200, 
            Direction.BUY, Operation.NEW));
       
        //direction amendment scenario
        trades.add(new Trade(5012, "ACC-106", 1, "ABC", 100, 
            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5012, "ACC-106", 2, "ABC", 50, 
            Direction.SELL, Operation.AMEND));
        trades.add(new Trade(5014, "ACC-106", 1, "ABC", 200, 
            Direction.BUY, Operation.NEW));
       
        //security + direction amendment scenario
        trades.add(new Trade(5015, "ACC-107", 1, "OLA", 100,  
            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5015, "ACC-107", 2, "META", 50, 
            Direction.SELL, Operation.AMEND));
        trades.add(new Trade(5016, "ACC-108", 1, "OLA", 200, 
            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5016, "ACC-108", 2, "META", 50, 
            Direction.BUY, Operation.AMEND));
        trades.add(new Trade(5016, "ACC-108", 3, "OLA", 200, 
            Direction.BUY, Operation.AMEND));
      
       
        //same security - one accoutn sale other buy
        trades.add(new Trade(5017, "ACC-109", 1, "BCD", 200, 
            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5018, "ACC-110", 2, "BCD", 200, 
            Direction.SELL, Operation.NEW));
       
        //same security - multiple amendments on quantity
        trades.add(new Trade(5019, "ACC-111", 1, "EFG", 50, 
            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5019, "ACC-111", 2, "EFG", 200, 
            Direction.BUY, Operation.AMEND));
        trades.add(new Trade(5019, "ACC-111", 3, "EFG", 250, 
            Direction.BUY, Operation.AMEND));
        trades.add(new Trade(5019, "ACC-111", 4, "EFG", 100, 
            Direction.BUY, Operation.AMEND));
       
       
        //Same Security - NEW MOD CANCEL test
        trades.add(new Trade(5020, "ACC-112", 1, "BES", 50, 
            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5020, "ACC-112", 2, "BES", 200, 

            Direction.BUY, Operation.AMEND));
        trades.add(new Trade(5020, "ACC-112", 3, "BES", 200, 

            Direction.BUY, Operation.CANCEL));
       
       
        //outofsequence trade events
        trades.add(new Trade(5019, "ACC-113", 1, "KBC", 100, 

            Direction.BUY, Operation.NEW));
        trades.add(new Trade(5019, "ACC-113", 2, "KBC", 150, 

            Direction.BUY, Operation.AMEND));
        trades.add(new Trade(5019, "ACC-113", 4, "KBC", 150, 

            Direction.BUY, Operation.CANCEL));
        trades.add(new Trade(5019, "ACC-113", 3, "KBC", 250, 

            Direction.BUY, Operation.AMEND));
       
        return trades;
    }
}