code: @VisibleForTesting
  	protected void assertCounterAmountMutatable(final String counterName, final CounterStatus counterStatus)
  	{
  		if (counterStatus != CounterStatus.AVAILABLE)
  		{
  			final String msg = String.format(
  				"Can't mutate the amount of counter '%s' because it's currently in the %s state but must be in in "
  					+ "the %s state!",
  				counterName, counterStatus.name(), CounterStatus.AVAILABLE);
  			throw new CounterNotMutableException(counterName, msg);
  		}
  	}
docs: Helper method to determine if a counter's incrementAmount can be mutated (incremented or decremented). In order
  for that to happen, the counter's status must be {@link CounterStatus#AVAILABLE}.
  
  @param counterName
  @param counterStatus
  @return