DelayedTimeProvider.kt

class DelayedTimeProvider(private val timeProvider: TimeProvider,
                          private val delayed: Delayed) : TimeProvider {
    override fun getTime(): Long = timeProvider.getTime() + delayed.get()
}

data class Delayed(private val time: Long, private val unit: TimeUnit) {
    fun get() = unit.toMillis(time)
}

TimeProvider.kt

interface TimeProvider {
    fun getTime(): Long
}

TimeToLive.kt

class TimeToLive(private val ttlTime: Long, private val unit: TimeUnit, private val timeProvider: TimeProvider) {
    fun isValid(time: Long): Boolean = (timeProvider.now() - time) <= unit.toMillis(ttlTime)
}