Exclude a transitive dependency with Gradle’s Kotlin DSL

Excluding a transitive dependency from something you depend on is often necessary to exclude unwanted libraries. Beware that the unwanted library may be included by more than one dependency.

To exclude JUnit 4 from spring-boot-starter-test (in favour of JUnit 5) simply do:

dependencies {
  testImplementation("org.springframework.boot:spring-boot-starter-test"){
    exclude("junit", "junit")
  }
}

Check that no other dependencies include JUnit 4:

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

Note the --configuration option. Be sure to specify the correct configuration. If unsure what configuration to use look at the output of any gradle task with the --info option. For example:

./gradlew projects --info

If you’re still unsure about configurations, just make sure this returns nothing:

./gradlew dependencies | grep junit