Setting Up Environment

In this tutorial, we are downloading and installing required softwares and tools. We will also start the project and set up for JUnit testing.

First of all, we need to install Java and development IDE to work with Java easily. For this tutorial, I am using Java 11. However, you use latest version of Java. It should most likely be backward compatible.

1. Download and install JDK. There are several Java Development Kit (JDK) available online. You can use Oracle JDK or OpenJDK published by major companies. Please, note that you need to install JDK and not JRE. You may also need to set up PATH variable to include Java binaries and JAVA_HOME variable to point to Java installation directory.
2. Install IntelliJ IDEA. This is Integrated Development Environment (IDE) for Java development. This is published by company Jetbrains and they have free Community version which you can download for free. Visit Jetbrains website and download IntelliJ IDEA Community Edition for your respective operating system.
3. Download and install maven. You can verify maven installation using mvn -version. This should show the currently installed maven version in your system.

Once these tools are installed, you can verify installation by opening terminal and typing java -version and it should return output with Java version installed in your system.

Creating new Maven Project

1. One you’ve launched IntelliJ IDEA, you can click New Project to create brand new project.

2. On the next screen, make sure “Maven Archetype” is selected and give your project a name. In this screenshot, I have named it junit-testing. In the second box, Location, you can change the location where you want to store this project in your system. For JDK, as you can see, I have selected Java 11.

3. In the middle section, select Maven Archetype and type org.apache.maven.archetypes:maven-archetype-archetype in this field. Towards, bottom click on Advanced Settings and provide groupId as com.example. This is like reverse domain name, so if you have any domain registered for yourself, you can use it in reverse order. For groupId, you can put junit-testing and for version modify it to 1.0.

4. Next click Create button.

Above steps will create basic skeleton project for Maven. The root directory the project contains pom.xml this is the file where we can specify the dependencies that our project depends on. In this case, specifically, we will need junit dependency. Currently, our project directory has below files and directories.

tree
├── pom.xml                          
└── src                              
    └── main                         
        └── resources                
            ├── META-INF             
            │   └── maven            
            │       └── archetype.xml
            └── archetype-resources  
                ├── pom.xml          
                └── src
                    ├── main
                    │   └── java
                    │       └── App.java
                    └── test
                        └── java
                            └── AppTest.java

Now, we have basic directory structure setup for Maven project. Remove the App.java file in src/main/java and AppTest.java in src/test/java directory respectively. Also delete the directory src/main/resources. We will write our own unit test and application code.

Adding JUnit Dependency

Next, we need to add JUnit dependency so that we can use it for our Unit testing. In this case, for maven, we can find the dependecy from Maven Repository.

Search for junit-jupiter, you will find several dependencies in maven. We just have to add junit-jupiter which is also referred to as Junit Jupiter (Aggregator) because it combines all JUnit dependencies. So, we don’t have to include each one explicitly.

In my case, I will add dependency like below in my pom.xml file.

1<dependencies>
2    <dependency>
3        <groupId>org.junit.jupiter</groupId>
4        <artifactId>junit-jupiter</artifactId>
5        <version>5.10.0</version>
6        <scope>test</scope>
7    </dependency>
8</dependencies>

At this point, we can reimport new dependencies in our POM file using Maven icon on the right side of your IDE. Click on Maven icon on the right panel and click “Reload all Maven Projects” icon as shown below.

This will download all Maven packages under External Libraries in the project navigation menu on the right hand side.

Add SureFire plugin

Another important feature of Maven is the ability to run tests using single command. This allows us to add this as one of the steps for CI (Continuous Integration) process. For this, we need to add one plugin into our POM file.

 1<build>
 2    <pluginManagement>
 3        <plugins>
 4            <plugin>
 5                <groupId>org.apache.maven.plugins</groupId>
 6                <artifactId>maven-surefire-plugin</artifactId>
 7                <version>3.1.2</version>
 8                <configuration>
 9                    <testFailureIgnore>true</testFailureIgnore>
10                </configuration>
11            </plugin>
12        </plugins>  
13    </pluginManagement>
14</build>

Run mvn clean install to set up and install all plugins and dependencies.

With this, we will be able to Maven tests using mvn clean test command.

You should get output like below.

[INFO] No tests to run.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  2.086 s
[INFO] Finished at: 2023-10-05T18:59:10-04:00
[INFO] ------------------------------------------------------------------------

With this, maven resolves depdendencies for JUnit. The next steps are to have some application code and we are ready to write our first unit tests.