Recall that we have a multi-module project, and the dependency versions are maintained in the parent POM under the dependencyManagement tag.

<dependencyManagement> 
    <dependencies> 
        ... 
        <dependency> 
            <groupId>junit</groupId> 
            <artifactId>junit</artifactId> 
            <version>4.12</version> 
            <scope>test</scope> 
        </dependency> 
    </dependencies> 
</dependencyManagement>

The scope of the dependency is test, which means that this library is needed only to compile the test code and during the execution of the test. The JUnit library will not make its way to the final released product; there is no need for it. If you find the JUnit library in some deployed production Web Archive (WAR) file, suspect that somebody was not properly managing the scopes of the libraries.

Maven supports the compilation and the execution of JUnit tests in the lifecycle of the project. If we want to execute the tests, only we can issue the mvn test command. The IDEs also support the execution of the unit tests. Usually, the same menu item that can be used to execute a class that has a public static main method can be used. If the class is a unit test utilizing JUnit, the IDE will recognize it and execute the tests and usually give a graphical feedback on what test was executing fine and which ones failed, and how.