*     positive values yield dates in the future.
   */
  private fun formatDate(
    delta: Long,
    timeUnit: TimeUnit,
  ): String? {
    return formatDate(Date(System.currentTimeMillis() + timeUnit.toMillis(delta)))
  }

  private fun formatDate(date: Date): String? {
    val rfc1123: DateFormat = SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US)
    rfc1123.timeZone = TimeZone.getTimeZone("GMT")

    lastTimestampNs = result.timestampNs

    if (eventClass != null) {
      assertThat(result).isInstanceOf(eventClass)
    }

    if (elapsedMs != -1L) {
      assertThat(
        TimeUnit.NANOSECONDS.toMillis(actualElapsedNs)
          .toDouble(),
      )
        .isCloseTo(elapsedMs.toDouble(), 100.0)
    }

    return result
  }

  fun recordedEventTypes() = eventSequence.map { it.name }