  We measure the void probability function (VPF) of galaxies in the Baryon
Oscillation Spectroscopic Survey (BOSS). The VPF provides complementary
information to standard two-point statistics in that it is sensitive to galaxy
bias in the most extreme underdensities in the cosmic web. Thus the VPF is
ideal for testing whether halo occupation of galaxies depends on large-scale
density, an effect known as galaxy assembly bias. We find that standard HOD
model---one parameterized by halo mass only---fit only to the two-point
function, accurately predicts the VPF. Additionally, for HOD models where
density dependence is explicitly incorporated, the best-fit models fit to the
combination of the correlation function and the VPF have zero density
dependence. Thus galaxy assembly bias is not a strong source of systematic
uncertaintiy when modeling the clustering of massive galaxies.
