  We present examples of validating components of an astrophysical simulation
code. Problems of stellar astrophysics are multi-dimensional and involve
physics acting on large ranges of length and time scales that are impossible to
include in macroscopic models on present computational resources. Simulating
these events thus necessitates the development of sub-grid-scale models and the
capability to post-process simulations with higher-fidelitymethods.We present
an overview of the problem of validating astrophysical models and simulations
illustrated with two examples. First, we present a study aimed at validating
hydrodynamicswith high energy density laboratory experiments probing shocks and
fluid instabilities. Second, we present an effort at validating code modules
for use in both macroscopic simulations of astrophysical events and for post
processing Lagrangian tracer particles to calculate detailed abundances from
thermonuclear reactions occurring during an event.
