  We consider a model of electrons in a finite topological insulator. We
numerically study the propagation of electronic wave-packets localized near
edges of the structure in the presence of defects and random disorder. We
compare the propagation with computations of the \emph{spectral localizer
index}: a spatially local topological index. We find that without disorder,
wave-packets propagate along boundaries between regions of differing spectral
localizer index with minimal loss, even in the presence of strong defects. With
disorder, wave-packets still propagate along boundaries between regions of
differing localizer index, but lose significant mass as they propagate. We also
find that with disorder, the \emph{localizer gap}, a measure of the localizer
index "strength", is generally smaller away from the boundary than without
disorder. Based on this result, we conjecture that wave-packets propagating
along boundaries between regions of differing spectral localizer index do not
lose significant mass whenever the localizer gap is sufficiently large on both
sides of the boundary.
