Generalized test tables: A powerful and intuitive specification language for reactive systems

With recent trends in manufacturing automation, such as Industry 4.0, control software in automated production systems becomes more and more complex and volatile, complicating and increasing importance of quality assurance. Test tables are a widely used and generally accepted means to intuitively specify test cases for automation software. However, each table only specifies a single software trace, whereas the actual software behavior may cover multiple similar traces not covered by the table. Within this work, we present a generalization concept for test tables allowing for bounded and unbounded repetition of steps, “don't-care” values, as well as calculations with earlier observed values. We provide a verification mechanism for checking conformance of an IEC 61131-3 PLC software with a generalized test table, making use of a state-of-the-art model checker. Our notation is inspired by widely-used paradigms found in spreadsheet applications. By an empirical study with mechanical engineering students, we show that the notation matches user expectations. A real-world example extracted from an industrial automation plant illustrates our approach.