Corda customising transaction validation - sharing validation

Validate.kt

private fun validate(transaction: BaseTransaction) {
  requireThat {
    val messages = transaction.outputsOfType<MessageState>()
    "There must be only one output message" using (messages.size == 1)
    val message = messages.single()
    "Message must contain the secret passphrase" using (message.contents.contains("I love Corda"))
  }
}