JUnit Testing For MySQL Project in Java

Last Updated : 23 Jul, 2025

For testing a software project, automated testing is always good and that will produce error-prone results. In the case of manual testing, there are possibilities of human errors. In this article let us take a sample project and let us see how to write JUnit test cases for it.

Example Project

Project Structure:

As this is the Maven-driven project, let us see

pom.xml

Relevant Maven dependency for JUnit. This has to be available in pom.xml

<dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.12</version>
  <scope>test</scope>
</dependency>

XML

<project xmlns="https://maven.apache.org/POM/4.0.0" 
         xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 
                             https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>geeksforgeeks</groupId>
  <artifactId>geeksforgeeks.jdbc.com</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>geeksforgeeks.jdbc.com</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <!-- MySQL usage dependency -->
      <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.6</version>
    </dependency>
    <!-- JUNIT dependency -->
   <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
  </dependencies>
</project>

Let us assume that MySQL got installed in the system and there is a database named "geeksforgeeks" is available

Let us see the important files of the project.

ds-connection.properties

# DataSource 
ds.database-driver=com.mysql.jdbc.Driver
ds.url=jdbc:mysql://localhost:3306/geeksforgeeks
ds.username=root
ds.password=***** # Provide your correct password

ConnectionClass.java

Java

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class ConnectionClass {
    public Connection getFileFromResources()
    {
        Properties prop = new Properties();
        try {
            prop.load(getClass().getResourceAsStream(
                "/resources/ds-connection.properties"));

            String dname
                = (String)prop.get("ds.database-driver");

            String dbConnUrl = (String)prop.get("ds.url");
            String dbUserName
                = (String)prop.get("ds.username");
            String dbPassword
                = (String)prop.get("ds.password");

            Class.forName(dname);
            Connection dbConn = DriverManager.getConnection(
                dbConnUrl, dbUserName, dbPassword);

            if (dbConn != null) {
                System.out.println("Connection Successful");
            }
            else {
                System.out.println(
                    "Failed to make connection!");
            }
            return dbConn;
        }
        catch (IOException e) {

            e.printStackTrace();
        }
        catch (ClassNotFoundException e) {

            e.printStackTrace();
        }
        catch (SQLException e) {
            e.printStackTrace();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static void close(Connection conn)
    {
        if (conn != null) {
            try {
                conn.close();
            }
            catch (SQLException e) {
                System.out.println(
                    "SQL Exception in close connection method");
            }
        }
    }

    public static void close(Statement stmt)
    {
        if (stmt != null) {
            try {
                stmt.close();
            }
            catch (SQLException e) {
                System.out.println(
                    "SQL Exception in close statement method");
            }
        }
    }

    public static void close(ResultSet rSet)
    {
        if (rSet != null) {
            try {
                rSet.close();
            }
            catch (SQLException e) {
                System.out.println(
                    "SQL Exception in close resultset method");
            }
        }
    }
}

Model Class:

Freelancer.java

Each and every field should match with the corresponding freelancer table(MySQL) column

Java

public class Freelancer {
    private int freelancerId;
    private String freelancerName;
    private int freelancerAge;
    private int pricePerHour;
    public int getFreelancerId() {
        return freelancerId;
    }
    public void setFreelancerId(int freelancerId) {
        this.freelancerId = freelancerId;
    }
    public String getFreelancerName() {
        return freelancerName;
    }
    public void setFreelancerName(String freelancerName) {
        this.freelancerName = freelancerName;
    }
    public int getFreelancerAge() {
        return freelancerAge;
    }
    public void setFreelancerAge(int freelancerAge) {
        this.freelancerAge = freelancerAge;
    }
    public int getPricePerHour() {
        return pricePerHour;
    }
    public void setPricePerHour(int pricePerHour) {
        this.pricePerHour = pricePerHour;
    }    
}

FreelancerQueries.java

Java

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class FreelancerQueries {
    // To get all the rows of Freelancer table data and
    // adding in the list
    public List<Freelancer> listFreelancerDetails()
    {
        ConnectionClass connClass = new ConnectionClass();
        Connection con = connClass.getFileFromResources();
        List<Freelancer> list = new ArrayList<Freelancer>();
        Freelancer freelancer = null;
        ResultSet rs = null;
        Statement stmt = null;
        // Write the SQL query
        String query = "select * from freelancer";
        try {
            stmt = con.createStatement();
            rs = stmt.executeQuery(query);
            // Iterate the whole resultset and add the data
            // in the list
            while (rs.next()) {
                freelancer = new Freelancer();
                freelancer.setFreelancerId(rs.getInt(1));
                freelancer.setFreelancerName(
                    rs.getString(2));
                freelancer.setFreelancerAge(rs.getInt(3));
                freelancer.setPricePerHour(rs.getInt(4));
                // System.out.println(rs.getInt(1) + " " +
                // rs.getString(2));
                list.add(freelancer);
            }
        }
        catch (SQLException e) {
            e.printStackTrace();
        }
        finally {
            connClass.close(con);
            connClass.close(stmt);
            connClass.close(rs);
        }
        return list;
    }
    // Retrieve Freelancer Name by Means of Freelancer Id
    public String getFreelancerNameById(int freelancerId)
    {
        ConnectionClass connClass = new ConnectionClass();
        Connection con = connClass.getFileFromResources();
        PreparedStatement pStmt = null;
        ResultSet rs = null;
        String freelancerName = null;
        try {
            // Retrieve the row for the matching
            // freelancerId
            String query
                = "select * from freelancer where freelancerId=?";
            pStmt = con.prepareStatement(query);
            pStmt.setInt(1, freelancerId);
            rs = pStmt.executeQuery();

            while (rs.next()) {
                // Get the freelancerName
                freelancerName = rs.getString(2);
                System.out.println(rs.getString(2));
            }
        }
        catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        finally {
            connClass.close(con);
            connClass.close(pStmt);
            connClass.close(rs);
        }
        return freelancerName;
    }
    // Retrieve PriceOerHour for the given freelanceId
    public int getFreelancerPricePerHour(int freelancerId)
    {
        ConnectionClass connClass = new ConnectionClass();
        Connection con = connClass.getFileFromResources();
        PreparedStatement pStmt = null;
        ResultSet rs = null;
        int pricePerHour = 0;
        try {
            String query
                = "select * from freelancer where freelancerId=?";
            pStmt = con.prepareStatement(query);
            pStmt.setInt(1, freelancerId);
            rs = pStmt.executeQuery();
            while (rs.next()) {
                pricePerHour = rs.getInt(4);
                System.out.println(pricePerHour);
            }
        }
        catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        finally {
            connClass.close(con);
            connClass.close(pStmt);
            connClass.close(rs);
        }
        return pricePerHour;
    }
}

Now, let us see the JUnit test case preparation file. Here we have to include positive, and negative scenarios for each and every requirement. Multiple assert statements we can write in a method and all should get passed and that will tell about our software code is correct in all aspects and for any test data, the written code will be correct.

AppTest.java

Each and every method has to start with @Test and inside the method, the methods written in "FreelancerQueries.java" should be called. Testcases can be written with

assertEquals (Equality checking)
assertNotEquals(Not equality checking)
assertTrue(Checking for True) etc.,

Java

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotEquals;
import java.util.List;
import org.junit.Test;

public class AppTest {
    FreelancerQueries freelancerQueriesObject = new FreelancerQueries();    
    
      @Test
    public void listFreelancerDetails_positive() {
         List<Freelancer> listFreelancerDetails = freelancerQueriesObject.listFreelancerDetails();
         // Checking whether totally 2 freelancers are available
         assertEquals(listFreelancerDetails.size(), 2);
         // Checking whether first freelancer id is 1
         assertEquals(listFreelancerDetails.get(0).getFreelancerId(),1);
         // Checking whether first freelancer name is Freelancer A
         assertEquals(listFreelancerDetails.get(0).getFreelancerName(),"Freelancer A");
         // Checking whether second  freelancer age is 20
         assertEquals(listFreelancerDetails.get(1).getFreelancerAge(),20);
         // Checking whether second  freelancer price per hour  is 2000
         assertEquals(listFreelancerDetails.get(1).getPricePerHour(),2000);
    }

    @Test
    public void listFreelancerDetails_negative() {
         List<Freelancer> listFreelancerDetails = freelancerQueriesObject.listFreelancerDetails();
         // As this is negative testing we need to check with assertNotEquals
         assertNotEquals(listFreelancerDetails.size(), 11);
         // Checking whether first freelancer id is not 10
         assertNotEquals(listFreelancerDetails.get(0).getFreelancerId(),10);
         // Checking whether first freelancer name is not Rachel
         assertNotEquals(listFreelancerDetails.get(0).getFreelancerName(),"Rachel");
         // Checking whether second  freelancer age is not 30
         assertNotEquals(listFreelancerDetails.get(1).getFreelancerAge(),30);
         // Checking whether second  freelancer price per hour  is not 4000
         assertNotEquals(listFreelancerDetails.get(0).getPricePerHour(),4000);
    }    
  
    @Test
    public void getFreelancerName_PositiveTestCase() {
         String freelancerName = freelancerQueriesObject.getFreelancerNameById(1);
         assertEquals(freelancerName, "Freelancer A");
         freelancerName = freelancerQueriesObject.getFreelancerNameById(2);
         assertEquals(freelancerName, "Freelancer B");
    }
  
    @Test
    public void getdFreelancerName_NegativeTestCase() {
         String freelancerName = freelancerQueriesObject.getFreelancerNameById(2);
         assertNotEquals(freelancerName, "Phoebe");
    }
    
    @Test
    public void getFirstFreelancerPricePerHour_PositiveTestCase() {
         int pricePerHour = freelancerQueriesObject.getFreelancerPricePerHour(1);
         assertEquals(pricePerHour, 1000);
    }    
  
    @Test
    public void getSecondFreelancerPricePerHour_NegativeTestCase() {
        int pricePerHour = freelancerQueriesObject.getFreelancerPricePerHour(2);
         assertNotEquals(pricePerHour, 5000);    
    }
  
}