This article reviews the use of the software program lp_solve version 5.5 for solving mixed-integer automated test assembly (ATA) problems. The program is freely available under Lesser General Public License 2 (LGPL2). It can be called from the statistical language R using the lpSolveAPI interface. Three empirical problems are presented to demonstrate how to use the program and interface to (a) simultaneously assemble multiple test forms with absolute targets for their test information functions, (b) assemble shadow tests for computerized adaptive testing, and (c) assemble multistage tests using relative targets for their test information functions, all subject to various quantitative and categorical constraints. The results of this study indicate that it is now possible for researchers and testing organizations to implement ATA for small to moderately sized test assembly problems using free software. (Contains 3 tables and 4 figures.)