Density discontinuity testing (a.k.a. manipulation testing) is commonly employed in regression discontinuity designs and other program evaluation settings to detect perfect self-selection (manipulation) around a cutoff where treatment/policy assignment changes. This package implements manipulation testing procedures using local polynomial density estimators: rddensity() constructs test statistics and p-values given a prespecified cutoff, rdbwdensity() performs data-driven bandwidth selection, and rdplotdensity() constructs density plots.