public static Object[] asUnwrappedArgumentArray(Object args) {
    return InvokerHelper.asUnwrappedArray(InvokerHelper.asArray(args).clone());
  }
If args is an array it is cloned and the clone is modified.
The original array is not changed.
spock-core/src/main/java/org/spockframework/runtime/GroovyRuntimeUtil.java