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Unit Testing Data Access Logic in Java

Most interviewers like Java candidates those who are passionate and experienced about writing unit tests. Any non trivial Java application will be making calls to database tables. So, here are a few questions and answers testing your ability to write unit tests to test data access layer.

Q1.

…

Unit Testing Servlet filter with Mockito

This assumes that you have gone through the basic JUnit & Mockito tutorials. Here is test class to “Unit Testing Servlet Filter”. The “HttpServletRequest“, “HttpServletResponse“, “FilterChain“, etc are mocked with Mockito. The Spring also provides classes like “

…

Unit testing Spring Transaction Management

Unit testing Spring transaction management –> i.e. commit & rollback scenarios as shown below. On a separate post, will do an integration test for the Spring transaction manager. The test class defines the transactional boundaries. Transaction Commit scenario

package com.myapp.dao;

import java.util.List;

import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.test.context.junit4.AbstractTransactionalJUnit4SpringContextTests;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.transaction.AfterTransaction;
import org.springframework.test.context.transaction.BeforeTransaction;
import org.springframework.test.context.transaction.TransactionConfiguration;
import org.springframework.transaction.annotation.Transactional;

import com.myapp.config.AppConfig;
import com.myapp.config.AppTestConfig;
import com.myapp.model.EventControl;
import com.myapp.model.common.MyAppType;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = { AppConfig.class, AppTestConfig.class })
@TransactionConfiguration(transactionManager = "transactionManager", defaultRollback = false)
public class EventControlDaoTxnCommitTest extends AbstractTransactionalJUnit4SpringContextTests {

    @Autowired
    EventControlDao eventControlDao;

    private static final String USER_ID = "AYYYY";
    private static final String EVENT_DATE = "20/10/2015";
    

    @BeforeTransaction
    public void beforeTransaction() {
        testEventControl(0);
    }

    @AfterTransaction
    public void afterTransaction() {
        testEventControl(1);
    }

    @Test
    @Transactional
    public void testEventControlCommit() {
        eventControlDao.create(getFsEventControl(USER_ID, EVENT_DATE));
    }
    
    private void testEventControl(int count) {
        List<EventControl> listEventControl = eventControlDao.findByValue(getPendingEventControl());
        Assert.assertEquals(count, listEventControl.size());
    }

    private EventControl getFsEventControl(String client, String eventKey) {
        EventControl fsEventControl = new EventControl();
        fsEventControl.setEventType(EventControl.EventType.BASIC);
        fsEventControl.setEventKey(EventControl.EventKey.USER_DATE);
        fsEventControl.setEventValue1(client);
        fsEventControl.setEventValue2(EVENT_DATE);
        return fsEventControl;
    }

    private EventControl getPendingEventControl() {
        EventControl ec = new EventControl();
        ec.setEventType(EventControl.EventType.BASIC);
        ec.setEventValue1(USER_ID);
        ec.setEventValue2(EVENT_DATE);
        ec.setEventStatus(EventControl.EventStatus.PENDING);
        return ec;
    }
}

package com.myapp.dao;

import java.util.List;

import org.junit.Assert;

import org.junit.Test;

import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.test.SpringApplicationConfiguration;

import org.springframework.test.context.junit4.AbstractTransactionalJUnit4SpringContextTests;

import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import org.springframework.test.context.transaction.AfterTransaction;

import org.springframework.test.context.transaction.BeforeTransaction;

import org.springframework.test.context.transaction.TransactionConfiguration;

import org.springframework.transaction.annotation.Transactional;

import com.myapp.config.AppConfig;

import com.myapp.config.AppTestConfig;

import com.myapp.model.EventControl;

import com.myapp.model.common.MyAppType;

@RunWith(SpringJUnit4ClassRunner.class)

@SpringApplicationConfiguration(classes = { AppConfig.class, AppTestConfig.class })

@TransactionConfiguration(transactionManager = "transactionManager", defaultRollback = false)

public class EventControlDaoTxnCommitTest extends AbstractTransactionalJUnit4SpringContextTests {

@Autowired

EventControlDao eventControlDao;

private static final String USER_ID = "AYYYY";

private static final String EVENT_DATE = "20/10/2015";

@BeforeTransaction

public void beforeTransaction() {

testEventControl(0);

}

@AfterTransaction

public void afterTransaction() {

testEventControl(1);

}

@Test

@Transactional

public void testEventControlCommit() {

eventControlDao.create(getFsEventControl(USER_ID, EVENT_DATE));

}

private void testEventControl(int count) {

List<EventControl> listEventControl = eventControlDao.findByValue(getPendingEventControl());

Assert.assertEquals(count, listEventControl.size());

}

private EventControl getFsEventControl(String client, String eventKey) {

EventControl fsEventControl = new EventControl();

fsEventControl.setEventType(EventControl.EventType.BASIC);

fsEventControl.setEventKey(EventControl.EventKey.USER_DATE);

fsEventControl.setEventValue1(client);

fsEventControl.setEventValue2(EVENT_DATE);

return fsEventControl;

}

private EventControl getPendingEventControl() {

EventControl ec = new EventControl();

ec.setEventType(EventControl.EventType.BASIC);

ec.setEventValue1(USER_ID);

ec.setEventValue2(EVENT_DATE);

ec.setEventStatus(EventControl.EventStatus.PENDING);

return ec;

}

Transaction Rolback scenario

package com.myapp.dao;

import java.util.List;

import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.test.annotation.Rollback;
import org.springframework.test.context.junit4.AbstractTransactionalJUnit4SpringContextTests;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.transaction.AfterTransaction;
import org.springframework.test.context.transaction.BeforeTransaction;
import org.springframework.test.context.transaction.TransactionConfiguration;
import org.springframework.transaction.annotation.Transactional;

importcom.myappconfig.AppConfig;
importcom.myappconfig.AppTestConfig;
importcom.myappmodel.EventControl;
import com.myapp.model.commonEventType;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = { AppConfig.class, AppTestConfig.class })
@TransactionConfiguration(transactionManager = "transactionManager", defaultRollback = false)
public class EventControlDaoTxnRollbackTest extends AbstractTransactionalJUnit4SpringContextTests {

    @Autowired
    EventControlDao eventControlDao;

    private static final String USER_ID = "AXXX";
    private static final String EVENT_DATE = "20/10/2015";

    @BeforeTransaction
    public void beforeTransaction() {
        testEventControl(0);
    }

    @AfterTransaction
    public void afterTransaction() {
        testEventControl(0);
    }

    @Test
    @Transactional
    @Rollback(true)
    public void testEventControlRollback() {
        eventControlDao.create(getFsEventControl(USER_ID, EVENT_DATE));
    }
    
    private void testEventControl(int count) {
        List<EventControl> listEventControl = eventControlDao.findByValue(getPendingEventControl());
        Assert.assertEquals(count, listEventControl.size());
    }

    private EventControl getFsEventControl(String clientId, String fsDate) {
        EventControl fsEventControl = new EventControl();
        fsEventControl.setEventType(EventControl.EventType.BASIC);
        fsEventControl.setEventKey(EventControl.EventKey.USER_DATE);
        fsEventControl.setEventValue1(clientId);
        fsEventControl.setEventValue2(fsDate);
        fsEventControl.setEventStatus(EventControl.EventStatus.PENDING);
        return fsEventControl;
    }

    private EventControl getPendingEventControl() {
        EventControl ec = new EventControl();
        ec.setEventType(EventControl.EventType.BASIC);
        ec.setEventValue1(USER_ID);
        ec.setEventValue2(EVENT_DATE);
        ec.setEventStatus(EventControl.EventStatus.PENDING);
        return ec;
    }
}

package com.myapp.dao;

import java.util.List;

import org.junit.Assert;

import org.junit.Test;

import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.test.SpringApplicationConfiguration;

import org.springframework.test.annotation.Rollback;

import org.springframework.test.context.junit4.AbstractTransactionalJUnit4SpringContextTests;

import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import org.springframework.test.context.transaction.AfterTransaction;

import org.springframework.test.context.transaction.BeforeTransaction;

import org.springframework.test.context.transaction.TransactionConfiguration;

import org.springframework.transaction.annotation.Transactional;

importcom.myappconfig.AppConfig;

importcom.myappconfig.AppTestConfig;

importcom.myappmodel.EventControl;

import com.myapp.model.commonEventType;

@RunWith(SpringJUnit4ClassRunner.class)

@SpringApplicationConfiguration(classes = { AppConfig.class, AppTestConfig.class })

@TransactionConfiguration(transactionManager = "transactionManager", defaultRollback = false)

public class EventControlDaoTxnRollbackTest extends AbstractTransactionalJUnit4SpringContextTests {

@Autowired

EventControlDao eventControlDao;

private static final String USER_ID = "AXXX";

private static final String EVENT_DATE = "20/10/2015";

@BeforeTransaction

public void beforeTransaction() {

testEventControl(0);

}

@AfterTransaction

public void afterTransaction() {

testEventControl(0);

}

@Test

@Transactional

@Rollback(true)

public void testEventControlRollback() {

eventControlDao.create(getFsEventControl(USER_ID, EVENT_DATE));

}

private void testEventControl(int count) {

List<EventControl> listEventControl = eventControlDao.findByValue(getPendingEventControl());

Assert.assertEquals(count, listEventControl.size());

}

private EventControl getFsEventControl(String clientId, String fsDate) {

EventControl fsEventControl = new EventControl();

fsEventControl.setEventType(EventControl.EventType.BASIC);

fsEventControl.setEventKey(EventControl.EventKey.USER_DATE);

fsEventControl.setEventValue1(clientId);

fsEventControl.setEventValue2(fsDate);

fsEventControl.setEventStatus(EventControl.EventStatus.PENDING);

return fsEventControl;

}

private EventControl getPendingEventControl() {

EventControl ec = new EventControl();

ec.setEventType(EventControl.EventType.BASIC);

ec.setEventValue1(USER_ID);

ec.setEventValue2(EVENT_DATE);

ec.setEventStatus(EventControl.EventStatus.PENDING);

return ec;

}

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What is wrong with this Java code? Heap Vs Stack, Thread safety & Synchronized

This post covers must know Java Multithreading basics – Heap Vs Stack, Thread-safety & Synchronization. When you have a multithreaded Java application, you need to code in a thread-safe manner. Java interviewers may ask you to detect thread-safety issues as discussed in here.

1.What is wrong with the following code?…

Why acquire skills & experience in low latency & Big Data? What specific skills are required?

According to Dice’s 2017 Salary Survey (PDF), those tech professionals who specialise in data warehousing, analytics, Big Data, low latency, and machine learning got paid big bucks for the past several years.

Working with data is not only about writing SQL queries….If you get an interesting role as a #dataengineer it can be lots of fun doing variety of things.

…

Why favour composition over inheritance?

This is not only one of the most popular Java OOP Interview Questions & Answers asked 90% of the time in job interviews, but also a key OOP concept you must know well.

The correct answer depends on the problem you are trying to solve, and the answer you give reveal a lot about your know-hows &

…

Working with a given input string & character processing

Q. Complete the following StringProcessingImpl.java” class ….. so that the unit tests shown below pass?

package com.passing.unittests;

public class StringProcessingImpl implements StringProcessing {

    public int getWordCount(String input) {
        return 0;
    }

    public int getCapitalsCount(String input) {
        return 0;
    }

    public String encode(String input) {
        return null;
    }

    public String removeRepeatedConsecutiveCharacters(String string, int consecutiveAllowedCount) {
        return null;
    }

    public String replaceRepeatedWordsWith(String input, String... replaceWord) {
        return null;
    }
}

package com.passing.unittests;

public class StringProcessingImpl implements StringProcessing {

public int getWordCount(String input) {

return 0;

}

public int getCapitalsCount(String input) {

return 0;

}

public String encode(String input) {

return null;

}

public String removeRepeatedConsecutiveCharacters(String string, int consecutiveAllowedCount) {

return null;

}

public String replaceRepeatedWordsWith(String input, String... replaceWord) {

return null;

}

Unit test

package com.passing.unittests;

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;


public class StringProcessingTest {

    private static final String INPUT = "Logic takes you from A to B, but imagination takes you everywhere";

    private StringProcessing sp = null;

    @Before
    public void init() {
        sp = new StringProcessingImpl();
    }

    @Test
    public void testgetWordCount() {
        Assert.assertEquals("Wrong", 12, sp.getWordCount(INPUT));
    }

    @Test
    public void testGetCapitalsCount() {
        Assert.assertEquals("Wrong", 3, sp.getCapitalsCount(INPUT));
    }

    @Test
    public void testEncode() {
        Assert.assertEquals("Wrong", "Ybtvp gnxrf lbh sebz N gb O, ohg vzntvangvba gnxrf lbh rireljurer",
            sp.encode(INPUT));
    }

    @Test
    public void testRemoveRepeatedConsecutiveCharacters() {
        Assert.assertEquals("Wrong", "blah Blah Blah",
            sp.removeRepeatedConsecutiveCharacters("blaah Blaaaah Blahhhh", 1));
        Assert.assertEquals("Wrong", "blaah Blaah Blahh",
            sp.removeRepeatedConsecutiveCharacters("blaah Blaaaah Blahhhh",2));
    }
    
    @Test
    public void testReplaceRepeatedWords() {
        Assert.assertEquals("Wrong", "Logic takes you from A to B, but imagination recognises us everywhere",
            sp.replaceRepeatedWordsWith (INPUT, "recognises", "us")); //takes -> recognises , you -> us
    }

}

package com.passing.unittests;

import org.junit.Assert;

import org.junit.Before;

import org.junit.Test;

public class StringProcessingTest {

private static final String INPUT = "Logic takes you from A to B, but imagination takes you everywhere";

private StringProcessing sp = null;

@Before

public void init() {

sp = new StringProcessingImpl();

}

@Test

public void testgetWordCount() {

Assert.assertEquals("Wrong", 12, sp.getWordCount(INPUT));

}

@Test

public void testGetCapitalsCount() {

Assert.assertEquals("Wrong", 3, sp.getCapitalsCount(INPUT));

}

@Test

public void testEncode() {

Assert.assertEquals("Wrong", "Ybtvp gnxrf lbh sebz N gb O, ohg vzntvangvba gnxrf lbh rireljurer",

sp.encode(INPUT));

}

@Test

public void testRemoveRepeatedConsecutiveCharacters() {

Assert.assertEquals("Wrong", "blah Blah Blah",

sp.removeRepeatedConsecutiveCharacters("blaah Blaaaah Blahhhh", 1));

Assert.assertEquals("Wrong", "blaah Blaah Blahh",

sp.removeRepeatedConsecutiveCharacters("blaah Blaaaah Blahhhh",2));

}

@Test

public void testReplaceRepeatedWords() {

Assert.assertEquals("Wrong", "Logic takes you from A to B, but imagination recognises us everywhere",

sp.replaceRepeatedWordsWith (INPUT, "recognises", "us")); //takes -> recognises , you -> us

}

Solution

package com.passing.unittests;

import java.util.HashSet;
import java.util.Set;

public class StringProcessingImpl implements StringProcessing {

    public int getWordCount(String input) {
        if(input == null || input.length() == 0){
            return 0;
        }
        
        String[] split = input.split("\\s+"); // regex to split on 1 or more spaces
        
        return split.length;
    }

    public int getCapitalsCount(String input) {
        if(input == null || input.length() == 0){
            return 0;
        }
        
        int counter = 0;
        
        char[] charArray = input.toCharArray();
        for (char c : charArray) {
            if(Character.isUpperCase(c)) {
                counter++;
            }
        }
        
        return counter;
    }

    /**
     *  System.out.println((int) ('Y' - 'L')); //13
        System.out.println((int) ('N' - 'A')); //13
     */
    public String encode(String input) {
        
        if(input == null || input.length() == 0){
            return input;
        }
        
        StringBuilder sb = new StringBuilder();

        for (char c : input.toCharArray()) {
            
            if (c >= 'a' && c <= 'm') {
               c += 13;
            }
            else if (c >= 'A' && c <= 'M'){
                c += 13;
            }
            else if (c >= 'n' && c <= 'z'){
                c -= 13;
            }
            else if (c >= 'M' && c <= 'Z'){
                c -= 13;
            }

            //System.out.println(c + " is " + n);
            sb.append(c);
        }

        return sb.toString();
    }

    public String removeRepeatedConsecutiveCharacters(String input, int consecutiveAllowedCount) {
        if(input == null || input.length() == 0){
            return input;
        }
        
        char[] charArray = input.toCharArray();
        char prev_c = ' ', cons_char_seen_count = 0;
        
        StringBuilder sb = new StringBuilder(input.length());
        
        for (char current_c : charArray) {
            if(current_c == prev_c){
                ++cons_char_seen_count;
            }
            else {
                cons_char_seen_count = 0; // resetting the count
                prev_c = current_c;
            }
            
            if(cons_char_seen_count < consecutiveAllowedCount){
              sb.append(current_c);   
            }
        }
        
        return sb.toString();
    }

    /**
     *  varargs is used with ...
     */
    public String replaceRepeatedWordsWith(String input, String... replaceWord) {
        if(input == null || input.length() == 0){
            return input;
        }
        
        Set<String> processedWords = new HashSet<String>(20);
        StringBuilder sb = new StringBuilder(50);
        
        int index = 0;
        
        for (String word : input.split("\\s+")) {
            if(!processedWords.contains(word)){
                sb.append(word + " ");
                processedWords.add(word);
            } else {
                sb.append(replaceWord[index] + " ");
                index++;
            }
        }
        
        return sb.toString().trim();
    }
}

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package com.passing.unittests;

import java.util.HashSet;

import java.util.Set;

public class StringProcessingImpl implements StringProcessing {

public int getWordCount(String input) {

if(input == null || input.length() == 0){

return 0;

}

String[] split = input.split("\\s+"); // regex to split on 1 or more spaces

return split.length;

}

public int getCapitalsCount(String input) {

if(input == null || input.length() == 0){

return 0;

}

int counter = 0;

char[] charArray = input.toCharArray();

for (char c : charArray) {

if(Character.isUpperCase(c)) {

counter++;

}

return counter;

}

/**

* System.out.println((int) ('Y' - 'L')); //13

System.out.println((int) ('N' - 'A')); //13

public String encode(String input) {

if(input == null || input.length() == 0){

return input;

}

StringBuilder sb = new StringBuilder();

for (char c : input.toCharArray()) {

if (c >= 'a' && c <= 'm') {

c += 13;

}

else if (c >= 'A' && c <= 'M'){

c += 13;

}

else if (c >= 'n' && c <= 'z'){

c -= 13;

}

else if (c >= 'M' && c <= 'Z'){

c -= 13;

}

//System.out.println(c + " is " + n);

sb.append(c);

}

return sb.toString();

}

public String removeRepeatedConsecutiveCharacters(String input, int consecutiveAllowedCount) {

if(input == null || input.length() == 0){

return input;

}

char[] charArray = input.toCharArray();

char prev_c = ' ', cons_char_seen_count = 0;

StringBuilder sb = new StringBuilder(input.length());

for (char current_c : charArray) {

if(current_c == prev_c){

++cons_char_seen_count;

}

else {

cons_char_seen_count = 0; // resetting the count

prev_c = current_c;

}

if(cons_char_seen_count < consecutiveAllowedCount){

sb.append(current_c);

}

return sb.toString();

}

/**

* varargs is used with ...

public String replaceRepeatedWordsWith(String input, String... replaceWord) {

if(input == null || input.length() == 0){

return input;

}

Set<String> processedWords = new HashSet<String>(20);

StringBuilder sb = new StringBuilder(50);

int index = 0;

for (String word : input.split("\\s+")) {

if(!processedWords.contains(word)){

sb.append(word + " ");

processedWords.add(word);

} else {

sb.append(replaceWord[index] + " ");

index++;

}

return sb.toString().trim();

}

Key points #1. The encode method is using the rot13 encoding that is used for hiding offensive material from accidental viewing, … Read more ›...

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Working with monetary values

Q. Complete the following “MonetaryProcessingImpl.java” class … so that the unit tests shown below pass? Skeleton code

package com.passing.unittests;

public final class Denomination {

    private long _dollarCount;
    private long _50CentCount;
    private long _20CentCount;
    private long _10CentCount;
    private long _5CentCount;

    public Denomination(long _dollarCount, long _50CentCount, 
                       long _20CentCount, long _10CentCount, long _5CentCount) {
        this._dollarCount = _dollarCount;
        this._50CentCount = _50CentCount;
        this._20CentCount = _20CentCount;
        this._10CentCount = _10CentCount;
        this._5CentCount = _5CentCount;
    }
    
    
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + (int) (_10CentCount ^ (_10CentCount >>> 32));
        result = prime * result + (int) (_20CentCount ^ (_20CentCount >>> 32));
        result = prime * result + (int) (_50CentCount ^ (_50CentCount >>> 32));
        result = prime * result + (int) (_5CentCount ^ (_5CentCount >>> 32));
        result = prime * result + (int) (_dollarCount ^ (_dollarCount >>> 32));
        return result;
    }


    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Denomination other = (Denomination) obj;
        if (_10CentCount != other._10CentCount)
            return false;
        if (_20CentCount != other._20CentCount)
            return false;
        if (_50CentCount != other._50CentCount)
            return false;
        if (_5CentCount != other._5CentCount)
            return false;
        if (_dollarCount != other._dollarCount)
            return false;
        return true;
    }

    public long get_dollarCount() {
        return _dollarCount;
    }

    public long get_50CentCount() {
        return _50CentCount;
    }

    public long get_20CentCount() {
        return _20CentCount;
    }

    public long get_10CentCount() {
        return _10CentCount;
    }

    public long get_5CentCount() {
        return _5CentCount;
    }  
}

package com.passing.unittests;

public final class Denomination {

private long _dollarCount;

private long _50CentCount;

private long _20CentCount;

private long _10CentCount;

private long _5CentCount;

public Denomination(long _dollarCount, long _50CentCount,

long _20CentCount, long _10CentCount, long _5CentCount) {

this._dollarCount = _dollarCount;

this._50CentCount = _50CentCount;

this._20CentCount = _20CentCount;

this._10CentCount = _10CentCount;

this._5CentCount = _5CentCount;

}

@Override

public int hashCode() {

final int prime = 31;

int result = 1;

result = prime * result + (int) (_10CentCount ^ (_10CentCount >>> 32));

result = prime * result + (int) (_20CentCount ^ (_20CentCount >>> 32));

result = prime * result + (int) (_50CentCount ^ (_50CentCount >>> 32));

result = prime * result + (int) (_5CentCount ^ (_5CentCount >>> 32));

result = prime * result + (int) (_dollarCount ^ (_dollarCount >>> 32));

return result;

}

@Override

public boolean equals(Object obj) {

if (this == obj)

return true;

if (obj == null)

return false;

if (getClass() != obj.getClass())

return false;

Denomination other = (Denomination) obj;

if (_10CentCount != other._10CentCount)

return false;

if (_20CentCount != other._20CentCount)

return false;

if (_50CentCount != other._50CentCount)

return false;

if (_5CentCount != other._5CentCount)

return false;

if (_dollarCount != other._dollarCount)

return false;

return true;

}

public long get_dollarCount() {

return _dollarCount;

}

public long get_50CentCount() {

return _50CentCount;

}

public long get_20CentCount() {

return _20CentCount;

}

public long get_10CentCount() {

return _10CentCount;

}

public long get_5CentCount() {

return _5CentCount;

}

package com.passing.unittests;

import java.math.BigDecimal;
import java.math.RoundingMode;

public interface MonetaryProcessing {
    
    abstract Denomination getDenominations(long amountInCents);
    
    abstract boolean isPositive(BigDecimal amount);

    abstract BigDecimal less(BigDecimal amount, BigDecimal amountToSubtract, boolean ignoreNegativeValue);
    
    abstract BigDecimal divide (BigDecimal input, BigDecimal divisor, RoundingMode roundingMode);
}

package com.passing.unittests;

import java.math.BigDecimal;

import java.math.RoundingMode;

public interface MonetaryProcessing {

abstract Denomination getDenominations(long amountInCents);

abstract boolean isPositive(BigDecimal amount);

abstract BigDecimal less(BigDecimal amount, BigDecimal amountToSubtract, boolean ignoreNegativeValue);

abstract BigDecimal divide (BigDecimal input, BigDecimal divisor, RoundingMode roundingMode);

}

package com.passing.unittests;

import java.math.BigDecimal;
import java.math.RoundingMode;


public class MonetaryProcessingImpl implements MonetaryProcessing {

    public Denomination getDenominations(long amountInCents) {
       return null;
    }

    public boolean isPositive(BigDecimal amount) {
        return false;
    }

    public BigDecimal less(BigDecimal balance, BigDecimal amountToSubtract, boolean ignoreNegativeValue) {
        return null;
    }

    public BigDecimal divide(BigDecimal input, BigDecimal divisor, RoundingMode roundingMode) {
       return null;
    }
   
}

package com.passing.unittests;

import java.math.BigDecimal;

import java.math.RoundingMode;

public class MonetaryProcessingImpl implements MonetaryProcessing {

public Denomination getDenominations(long amountInCents) {

return null;

}

public boolean isPositive(BigDecimal amount) {

return false;

}

public BigDecimal less(BigDecimal balance, BigDecimal amountToSubtract, boolean ignoreNegativeValue) {

return null;

}

public BigDecimal divide(BigDecimal input, BigDecimal divisor, RoundingMode roundingMode) {

return null;

}

The unit test that fails

package com.passing.unittests;

import java.math.BigDecimal;
import java.math.RoundingMode;

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

public class MonetaryProcessingTest {

    private MonetaryProcessing mp = null;

    @Before
    public void init() {
        mp = new MonetaryProcessingImpl();
    }

    @Test
    public void testGetDenominations() {
        Denomination denomination = new Denomination(9, 1, 1, 0, 1);
        Assert.assertEquals("Wrong", denomination, mp.getDenominations(975));
    }
    
    @Test(expected=IllegalArgumentException.class)
    public void testNegativeGetDenominations() {
       mp.getDenominations(0);
    }

    
    @Test
    public void testLess() {
        Assert.assertEquals("Wrong", BigDecimal.valueOf(875.00),  
            mp.less(BigDecimal.valueOf(900.00), BigDecimal.valueOf(25.00), false)); 
    }
    
    @Test
    public void testLess2() {
        Assert.assertEquals("Wrong", BigDecimal.valueOf(-925.00),  
            mp.less(BigDecimal.valueOf(-900.00), BigDecimal.valueOf(25.00), false)); 
    }
    
    
    @Test
    public void testLess3() {
        Assert.assertEquals("Wrong", BigDecimal.valueOf(-900.00),  
            mp.less(BigDecimal.valueOf(-900.00), BigDecimal.valueOf(25.00), true)); 
    }
    
    @Test(expected=IllegalArgumentException.class)
    public void testLessNegativeTest() {
        Assert.assertEquals("Wrong", BigDecimal.valueOf(-900.00),  
            mp.less(BigDecimal.valueOf(-900.00), BigDecimal.valueOf(-25.00), true)); 
    }
    
    
    @Test
    public void testDevide() {
        Assert.assertEquals("Wrong", BigDecimal.valueOf(3.14),  
            mp.divide(BigDecimal.valueOf(22.00), BigDecimal.valueOf(7.00), RoundingMode.HALF_EVEN)); 
    }
    
    
    @Test(expected=IllegalArgumentException.class)
    public void testDevideHegativeTest() {
        Assert.assertEquals("Wrong", BigDecimal.valueOf(3.14),  
            mp.divide(BigDecimal.valueOf(22.00), BigDecimal.valueOf(-7.00), RoundingMode.HALF_EVEN)); 
    }  
}

package com.passing.unittests;

import java.math.BigDecimal;

import java.math.RoundingMode;

import org.junit.Assert;

import org.junit.Before;

import org.junit.Test;

public class MonetaryProcessingTest {

private MonetaryProcessing mp = null;

@Before

public void init() {

mp = new MonetaryProcessingImpl();

}

@Test

public void testGetDenominations() {

Denomination denomination = new Denomination(9, 1, 1, 0, 1);

Assert.assertEquals("Wrong", denomination, mp.getDenominations(975));

}

@Test(expected=IllegalArgumentException.class)

public void testNegativeGetDenominations() {

mp.getDenominations(0);

}

@Test

public void testLess() {

Assert.assertEquals("Wrong", BigDecimal.valueOf(875.00),

mp.less(BigDecimal.valueOf(900.00), BigDecimal.valueOf(25.00), false));

}

@Test

public void testLess2() {

Assert.assertEquals("Wrong", BigDecimal.valueOf(-925.00),

mp.less(BigDecimal.valueOf(-900.00), BigDecimal.valueOf(25.00), false));

}

@Test

public void testLess3() {

Assert.assertEquals("Wrong", BigDecimal.valueOf(-900.00),

mp.less(BigDecimal.valueOf(-900.00), BigDecimal.valueOf(25.00), true));

}

@Test(expected=IllegalArgumentException.class)

public void testLessNegativeTest() {

Assert.assertEquals("Wrong", BigDecimal.valueOf(-900.00),

mp.less(BigDecimal.valueOf(-900.00), BigDecimal.valueOf(-25.00), true));

}

@Test

public void testDevide() {

Assert.assertEquals("Wrong", BigDecimal.valueOf(3.14),

mp.divide(BigDecimal.valueOf(22.00), BigDecimal.valueOf(7.00), RoundingMode.HALF_EVEN));

}

@Test(expected=IllegalArgumentException.class)

public void testDevideHegativeTest() {

Assert.assertEquals("Wrong", BigDecimal.valueOf(3.14),

mp.divide(BigDecimal.valueOf(22.00), BigDecimal.valueOf(-7.00), RoundingMode.HALF_EVEN));

}

A. Code that passes the test cases

package com.passing.unittests;

import java.math.BigDecimal;
import java.math.RoundingMode;


public class MonetaryProcessingImpl implements MonetaryProcessing {

    /**
     * the comments are for input of 975  cents
     */
    public Denomination getDenominations(long amountInCents) {
        
        if(amountInCents <= 0){
            throw new IllegalArgumentException("Invalid amount in cents: " + amountInCents);
        }
        
       long varDollarCount, var50CentCount, var20CentCount, var10CentCount, var5CentCount = 0;
       long balance = amountInCents;
       
       varDollarCount = balance/100; //9
       balance = balance%100; // 75
       
       var50CentCount = balance/50;   //1
       balance = balance%50; //25
       
       var20CentCount = balance/20; //1 
       balance = balance%20; //5
       
       var10CentCount = balance/10; //0
       balance = balance%10; //5
       
       var5CentCount = balance/5; //1
       balance = balance%5; //0
       
        
       return new Denomination(varDollarCount, var50CentCount, var20CentCount, var10CentCount, var5CentCount);
    }

    public boolean isPositive(BigDecimal amount) {
        return amount != null && amount.signum() == 1;
    }

    public BigDecimal less(BigDecimal balance, BigDecimal amountToSubtract, boolean ignoreNegativeValue) {
        
        if(amountToSubtract != null && amountToSubtract.signum() == -1){
            throw new IllegalArgumentException("Amount to sbtract cannot be -ve: " + amountToSubtract);
        }
        
        if (isPositive(balance) || !ignoreNegativeValue) {
            balance = balance.subtract(amountToSubtract);
        }
        
        return balance;
    }

    public BigDecimal divide(BigDecimal input, BigDecimal divisor, RoundingMode roundingMode) {
       if(input == null || divisor == null){
           throw new IllegalArgumentException("Invalid input");
       }
       
       if (divisor.compareTo(BigDecimal.ZERO) == 0 || divisor.compareTo(BigDecimal.ZERO) == -1){
           throw new IllegalArgumentException("Divisor cannot be zero or negative: " +  divisor);
       }
       
        return input.divide(divisor, 2, roundingMode);
    }  
}

package com.passing.unittests;

import java.math.BigDecimal;

import java.math.RoundingMode;

public class MonetaryProcessingImpl implements MonetaryProcessing {

/**

* the comments are for input of 975 cents

public Denomination getDenominations(long amountInCents) {

if(amountInCents <= 0){

throw new IllegalArgumentException("Invalid amount in cents: " + amountInCents);

}

long varDollarCount, var50CentCount, var20CentCount, var10CentCount, var5CentCount = 0;

long balance = amountInCents;

varDollarCount = balance/100; //9

balance = balance%100; // 75

var50CentCount = balance/50; //1

balance = balance%50; //25

var20CentCount = balance/20; //1

balance = balance%20; //5

var10CentCount = balance/10; //0

balance = balance%10; //5

var5CentCount = balance/5; //1

balance = balance%5; //0

return new Denomination(varDollarCount, var50CentCount, var20CentCount, var10CentCount, var5CentCount);

}

public boolean isPositive(BigDecimal amount) {

return amount != null && amount.signum() == 1;

}

public BigDecimal less(BigDecimal balance, BigDecimal amountToSubtract, boolean ignoreNegativeValue) {

if(amountToSubtract != null && amountToSubtract.signum() == -1){

throw new IllegalArgumentException("Amount to sbtract cannot be -ve: " + amountToSubtract);

}

if (isPositive(balance) || !ignoreNegativeValue) {

balance = balance.subtract(amountToSubtract);

}

return balance;

}

public BigDecimal divide(BigDecimal input, BigDecimal divisor, RoundingMode roundingMode) {

if(input == null || divisor == null){

throw new IllegalArgumentException("Invalid input");

}

if (divisor.compareTo(BigDecimal.ZERO) == 0 || divisor.compareTo(BigDecimal.ZERO) == -1){

throw new IllegalArgumentException("Divisor cannot be zero or negative: " + divisor);

}

return input.divide(divisor, 2, roundingMode);

}

Key Points Take note that test cases test for exceptions being thrown as well. … Read...

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XMPP, MQTT and Web Sockets protocols for building messaging & chat applications

These interview Q&As are handy if you are asked to design an instant messaging application. WhatsApp, Facebook Messenger, WebChat, Slack, Viber, etc are instant messaging applications. Microsoft Teams has an instant messaging platform with features such as instant chat, emojis, GIFs, rich-text editing, threaded conversations, plus the ability to share...

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A1. YAML Ain’t Markup Language. It is a human friendly data serialization standard for all programming languages. A YAML file has an extension of “.yml“.

Q2. What are the 3 rules of YAML?

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