A theory of regression testing for behaviourally compatible object types Research Articles.pdfVIP

A Theory of Regression Testing for Behaviourally Compatible Object Types Anthony J H Simons Department of Computer Science, University of Sheffield, Regent Court, 2 11 Portobello Street, Sheffield S1 4DP, United Kingdom A .Simons@dcs.shef.ac.uk http ://www.dcs.shef.ac.uk/~ajhs/ Abstract. This paper presents a behavioural theory of obj ect compatibility, based on the refinement of obj ect states. The theory predicts that only certain models of state refinement yield compatible types, dictating the legitimate de- sign styles to be adopted in obj ect statecharts. The theory also predicts that standard practices in regression testing are inadequate. Functionally complete test-sets that are applied as regression tests to subtype obj ects are usually ex- pected to cover the state-space of the original type, even if they do not cover transitions and states introduced in the subtype. However, such regression test- ing is proven to cover strictly less than this in the new context and so provides much weaker guarantees than was previously expected. Instead, a retesting model based on automatic test regeneration is required to guarantee equivalent levels of correctness. Keywords: Obj ect-oriented, behavioural subtyping, state refinement, state- based testing, regression testing, test generation, testing adequacy. 1 Introduction Practical obj ect-oriented unit testing is influenced considerably by the non-intrusive testing philosophy of McGregor et al [1, 2]. In this approach, every obj ect under test (OUT) has a corresponding test-harness obj ect (THO), which encapsulates all the tes