Step 1: Create the source code

In an empty directory on your local computer or instance, create this directory structure.

(root directory name)
    `-- src
         |-- main
         |     `-- java
         `-- test
               `-- java

Using a text editor of your choice, create this file, name it MessageUtil.java, and then save it in the src/main/java directory.

public class MessageUtil {
  private String message;

  public MessageUtil(String message) {
    this.message = message;
  }

  public String printMessage() {
    System.out.println(message);
    return message;
  }

  public String salutationMessage() {
    message = "Hi!" + message;
    System.out.println(message);
    return message;
  }
}

This class file creates as output the string of characters passed into it. The MessageUtil constructor sets the string of characters. The printMessage method creates the output. The salutationMessage method outputs Hi! followed by the string of characters.

Create this file, name it TestMessageUtil.java, and then save it in the /src/test/java directory.

import org.junit.Test;
import org.junit.Ignore;
import static org.junit.Assert.assertEquals;

public class TestMessageUtil {

  String message = "Robert";    
  MessageUtil messageUtil = new MessageUtil(message);
   
  @Test
  public void testPrintMessage() {      
    System.out.println("Inside testPrintMessage()");     
    assertEquals(message,messageUtil.printMessage());
  }

  @Test
  public void testSalutationMessage() {
    System.out.println("Inside testSalutationMessage()");
    message = "Hi!" + "Robert";
    assertEquals(message,messageUtil.salutationMessage());
  }
}

This class file sets the message variable in the MessageUtil class to Robert. It then tests to see if the message variable was successfully set by checking whether the strings Robert and Hi!Robert appear in the output.

Create this file, name it pom.xml, and then save it in the root (top level) directory.

<project xmlns="http://maven.apache.org/POM/4.0.0" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.example</groupId>
  <artifactId>messageUtil</artifactId>
  <version>1.0</version>
  <packaging>jar</packaging>
  <name>Message Utility Java Sample App</name>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>	
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.0</version>
      </plugin>
    </plugins>
  </build>
</project>

Apache Maven uses the instructions in this file to convert the MessageUtil.java and TestMessageUtil.java files into a file named messageUtil-1.0.jar and then run the specified tests.