In a task

tasks.named<ShadowJar>("shadowJar") {
  // with the set
  archiveBaseName.set("test")
}

or DSL style

tasks.test {
    failFast = true;
}

or

val testTask = tasks.getByName<Test>("test")
testTask.failFast = true;

In a configure block

configure<MyExtension> {
 message = "Hi"
}

In a the

the<GreetingPluginExtension>().message = "Hi from Gradle"