MSTest: An R-Package for Testing Markov Switching Models Staff working paper 2026-7 Gabriel Rodriguez Rondon, Jean-Marie Dufour We present the R package MSTest, which implements hypothesis testing procedures to determine the number of regimes in Markov switching models. The package provides several testing frameworks, including Monte Carlo likelihood ratio tests, moment-based tests, parameter stability tests, and classical likelihood ratio procedures. Content Type(s): Staff research, Staff working papers JEL Code(s): C, C1, C12, C15, C18, C6, C63, C8, C87 Research Theme(s): Models and tools, Econometric, statistical and computational methods, Economic models, Monetary policy, Real economy and forecasting