How to properly ignore Junit 4 in Gradle and Maven

#testing #java #gradle

Jump to the best example here for Gradle and Maven

Problem

Quite a lot of Java dependencies bring Junit 4 or Junit vintage engine as a transitive dependency.

As well as Junit vintage engine is designed to integrate 4 and 5 version, it allows to use both at the same time. When you want to finally migrate, it leads to problems such as:

Runtime issues: a junit4 class not found
A test has run, but no coverage aggregated
Not concise annotations usage

Solution

All these problems have only one proper solution:

Use one particular version of Junit to prevent misleading and misusage

Here I focus on the latest - Junit 5 version usage, hence, excluding of Junit 4.

One of the options is to ignore this dependency from a specific dependency:

testImplementation('org.springframework.boot:spring-boot-starter-test') {
    exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'  
}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
    <exclusions>
      <exclusion>
        <groupId>org.junit.vintage</groupId>
        <artifactId>junit-vintage-engine</artifactId>
      </exclusion>
    </exclusions>
  </dependency>

But, it requires you to know which dependency brings unpleasant dependency for you. In this case, you can use this command to track:

./gradlew dependencyInsight --dependency "junit:junit" --configuration "testCompileClasspath"

Another option is to exclude not necessary dependencies from all the configurations. It leads you another problems such as: some library still requires Junit 4 / vintage. But, the compilation / runtime reflection errors actually only makes these dependencies visual and help to mark explicitly those Java modules, that still require on any reason to work with a legacy library.

Gradle:

Having configurations in Gradle it is easy to exclude a dependency in one particular place:

/* for all the configurations */
configurations {
  all {
    /* only junit 5 should be used */
    exclude group: 'junit', module: 'junit'
    exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
  }
}

/* for a particular test module */
configurations {
  testCompile {
  /* only junit 5 should be used */
    exclude group: 'junit', module: 'junit'
    exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
  }
  testRuntime {
    /* only junit 5 should be used */
    exclude group: 'junit', module: 'junit'
    exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
  }
}