  We define an appropriate problem for benchmarking dust emissivity
calculations in the context of radiative transfer (RT) simulations,
specifically including the emission from stochastically heated dust grains. Our
aim is to provide a self-contained guide for implementors of such
functionality, and to offer insights in the effects of the various
approximations and heuristics implemented by the participating codes to
accelerate the calculations. The benchmark problem definition includes the
optical and calorimetric material properties, and the grain size distributions,
for a typical astronomical dust mixture with silicate, graphite and PAH
components; a series of analytically defined radiation fields to which the dust
population is to be exposed; and instructions for the desired output. We
process this problem using six RT codes participating in this benchmark effort,
and compare the results to a reference solution computed with the publicly
available dust emission code DustEM. The participating codes implement
different heuristics to keep the calculation time at an acceptable level. We
study the effects of these mechanisms on the calculated solutions, and report
on the level of (dis)agreement between the participating codes. For all but the
most extreme input fields, we find agreement within 10% across the important
wavelength range from 3 to 1000 micron. We conclude that the relevant modules
in RT codes can and do produce fairly consistent results for the emissivity
spectra of stochastically heated dust grains.
