What is the test for overturning a parole revocation order on the grounds of insufficient evidence to satisfy due process standards?

On appeal, defendant argues that that the parole revocation order must be reversed "on the ground of insufficient evidence to satisfy due process standards because the prosecution failed to satisfy its burden to prove . . . that appellant violated his parole by committing 'battery [of a] spouse/child." (All caps. omitted.) The People contend that the order should be affirmed because "the trial court was not required to find battery." We need not address the People's contention because, even if defendant were denied due process because the prosecution failed to prove and the trial court failed to find that a battery had occurred, the alleged error is harmless beyond a reasonable doubt. Constitutional errors are subject to federal harmless error analysis under Chapman v. California (1967) 386 U.S. 18, 24.