} else {
      // count how many bytes we'll need to express the length.
      val lengthBitCount = 64 - java.lang.Long.numberOfLeadingZeros(length)
      val lengthByteCount = (lengthBitCount + 7) / 8
      sink.writeByte(0b1000_0000 or lengthByteCount)
      for (shift in (lengthByteCount - 1) * 8 downTo 0 step 8) {
        sink.writeByte((length shr shift).toInt())
      }
    }

    // Write the payload.

    stopwatch.reset();
    assertFalse(stopwatch.isRunning());
    ticker.advance(3);
    assertEquals(0, stopwatch.elapsed(NANOSECONDS));
  }

  public void testElapsed_whileRunning() {
    ticker.advance(78);
    stopwatch.start();
    assertEquals(0, stopwatch.elapsed(NANOSECONDS));

    ticker.advance(345);
    assertEquals(345, stopwatch.elapsed(NANOSECONDS));
  }

  public void testElapsed_notRunning() {