Test generation from state based use case models

Abstract

We present a strategy for the automatic generation of test cases from parametrised use case templates that capture control flow, state, input and output. Our approach allows test scenario selection based on particular traces or states of the model. The templates are internally represented as CSP processes with explicit input and output alphabets, and test generation is expressed as counter-examples of refinement checking, mechanised using the FDR tool. Soundness is addressed through an input–output conformance relation formally defined in the CSP traces model. This purely process algebraic characterisation of testing has some potential advantages, mainly an easy automation of conformance verification and test case generation via model checking, without the need to develop any explicit algorithm.

A Suspension-Trace Semantics for CSP

“…Previous work [7], [19] explored test generation and compositional verification in the context of CSP, distinguishing input and output events. In those works, a relation cspio was defined and used for test-case generation via counterexamples of refinement in the traces model.…”

“…However, no formal account of suspension traces was provided and, as a consequence, no proper treatment of quiescence was given. The work here is a formal basis to justify the syntactic encodings in [7], [19].…”

“…As shown in [7], if all quiescences are identified in the traces as the special output δ, then cspioco can be verified as a tracesrefinement assertion. P cspioco Q holds if, and only if,…”

“…Recently, CSP has been used to encode the testing theory of IOLTS with ioco, with the CSP refinement model checker FDR used as a technology to generate tests [7]. In that work, a notion of IO process is defined, which partitions the alphabet of a process into input and output events.…”

“…This is the traditional model used for characterisation of ioco (in the context of input-output labelled transition systems). With this new model for CSP, we can reason about arbitrary processes using ioco rather than the restricted class of IO processes from [7]. In addition, our semantics gives the traditional CSP operators a different denotational view that caters for inputs and outputs.…”