“…Because of the use of a computer and the complexity of testing constraints (e.g., exposure control, content balance), simulation plays an important role in CAT research and practice. Researchers and test developers have been using the R package catR (Magis & Raîche, 2011) for CAT simulation—examples are Graf et al (2017), Oppl et al (2017), and Seo and Choi (2018), just to name a few. The R package catR (as of version 3.16), however, has a flaw that can potentially invalidate related simulation results.…”