Reactis® is a suite of tools produced by Reactive Systems, Inc. (RSI), for automated test generation from, and verification of, systems given in either the modeling languages MATLAB® / Simulink® / Stateflow® of The MathWorks, Inc., or ANSI C. RSI was founded by three of the authors of this paper in 1999, with the first release of Reactis coming in 2002; the tools are used in the testing and validation of embedded control systems in a variety of industries, including automotive and aerospace / defense. This paper traces the development of the Reactis tool suite from earlier research on model-checking tools undertaken by the authors and others, highlighting the importance of both the foundational basis of Reactis and the essential adaptations and extensions needed for a commercially successful product.