Run this script in the Jenkins console to get the all the plugin dependencies for use with the Job DSL and Jenkins Test Harness..

script.groovy

Jenkins.instance.pluginManager.activePlugins.sort { it.shortName }.each { plugin ->     
    def manifest = plugin.manifest
    String groupId = manifest.mainAttributes.getValue('Group-Id')
    String artifactId = manifest.mainAttributes.getValue('Extension-Name')
    String version = manifest.mainAttributes.getValue('Implementation-Version')
    if (groupId && artifactId && version) {
        println "testPlugins '$groupId:$artifactId:$version'"
    }
}

script2.groovy

String pluginName = 'workflow-cps-global-lib'

def mainPlugin = Jenkins.instance.pluginManager.getPlugin(pluginName)

List pluginWithDependencies = [mainPlugin]
if (mainPlugin.hasDependencies()) {
  pluginWithDependencies.addAll mainPlugin.dependencies.collect { Jenkins.instance.pluginManager.getPlugin it.shortName }
}
pluginWithDependencies.each { plugin ->     
    def manifest = plugin.manifest
    String groupId = manifest.mainAttributes.getValue('Group-Id')
    String artifactId = manifest.mainAttributes.getValue('Extension-Name')
    String version = manifest.mainAttributes.getValue('Implementation-Version')
    if (groupId && artifactId && version) {
        println "testPlugins '$groupId:$artifactId:$version'"
    }
}