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Regulatory standards for engineering safety-critical systems often demand both traceable requirements and specification-based testing, during development. Requirements are often written in natural language, yet for specification purposes, this may be supplemented by formal or semi-formal descriptions, to increase clarity. However, the choice of notation of the latter is often constrained by the training, skills, and preferences of the designers.The Easy Approach to Requirements Syntax (EARS) addresses the inherent imprecision of natural language requirements with respect to potential ambiguity and lack of accuracy. This paper investigates requirement formalization using EARS and specification-based testing of embedded software written in the IEC 61131-3 language, a programming standard used for developing Programmable Logic Controllers (PLC). Further, we investigate, by means of an experiment, how human participants translate natural language requirements into EARS and how they use the latter to test PLC software. We report our observations during the experiments, including the type of EARS patterns participants use to structure natural language requirements and challenges during the specification phase, as well as present the results of testing based on EARS-formalized requirements.