Creating a Custom ShadowJar Task

The built in shadowJar task only provides an output for the main source set of the project. It is possible to add arbitrary ShadowJar tasks to a project. When doing so, ensure that the configurations property is specified to inform Shadow which dependencies to merge into the output.

KotlinGroovy

val testShadowJar by tasks.registering(com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar::class) {
  group = LifecycleBasePlugin.BUILD_GROUP
  description = "Create a combined JAR of project and test dependencies"

  archiveClassifier = "tests"
  from(sourceSets.test.map { it.output })
  configurations = project.configurations.testRuntimeClasspath.map { listOf(it) }

  manifest {
    // Optionally, set the main class for the JAR.
    attributes(mapOf("Main-Class" to "test.Main"))
    // You can also set other attributes here.
  }
}

// Optionally, make the `assemble` task depend on the new task.
tasks.assemble {
  dependsOn(testShadowJar)
}

def testShadowJar = tasks.register('testShadowJar', com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar) {
  group = LifecycleBasePlugin.BUILD_GROUP
  description = 'Create a combined JAR of project and test dependencies'

  archiveClassifier = 'tests'
  from sourceSets.named('test').map { it.output }
  configurations = project.configurations.named('testRuntimeClasspath').map { [it] }

  manifest {
    // Optionally, set the main class for the JAR.
    attributes 'Main-Class': 'test.Main'
    // You can also set other attributes here.
  }
}

// Optionally, make the `assemble` task depend on the new task.
tasks.named('assemble') {
  dependsOn testShadowJar
}

The code snippet above will generate a shadowed JAR containing both the main and test sources as well as all testRuntimeOnly and testImplementation dependencies. The file is output to build/libs/<project>-<version>-tests.jar.