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 (opens new window) tasks to a project. When doing so, ensure that the configurations property is specified to inform Shadow which dependencies to merge into the output.

// Shadowing Test Sources and Dependencies
task testJar(type: com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar) {
  archiveClassifier.set("tests")
  from sourceSets.test.output
  configurations = [project.configurations.testRuntimeClasspath]
}

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.