f.realSum += d
}

func (f *fakeMetrics) Reset() []metrics.Registerable {
	f.realSum = 0
	originalResettable, ok := f.original.(resettable)
	if !ok {
		panic("wrapped metrics must implement resettable")
	}
	return originalResettable.Reset()
}

type resettable interface {
	Reset() []metrics.Registerable
}

func TestMetrics(t *testing.T) {

    }

    private void initCalculatedValues() {
        // TODO: We wrap the CalculatedValues in an AtomicReference so that we can reset their state, however
        //       CalculatedValues are not resettable for a reason. This is a pretty terrible hack.
        //       We should get rid of reevaluate entirely, so that we do not need these AtomicReferences.

One-shot iterators have the following limitations:

* They do not support parameterization: all logic for creating the underlying
  dataset must be bundled in the `dataset_factory` function.
* They are not resettable. Once a one-shot iterator reaches the end of its
  underlying dataset, subsequent "IteratorGetNext" operations on that
  iterator will always produce an `OutOfRange` error.