Processes, Systems & Tests: Defining Contextual Equivalences

In this position paper, we would like to offer and defend a new template study equivalences between programs -- in the particular framework of process algebras for concurrent computation.We believe that our layered model development will clarify distinction is too often left implicit tasks duties programmer tester. It also enlighten pre-existing issues have been running across as diverse calculus communicating systems, $\pi$-calculus its distributed version or mobile ambients.Our starts by subdividing notion itself three conceptually separated entities, call \emph{Processes}, \emph{Systems} \emph{Tests}. While role what can be observed subtleties definitions congruences intensively studied, fact \emph{not every tested}, \emph{the tester should access different set tools than programmer} curiously out, at least not formally discussed.We argue blind spot comes from under-specification contexts environments which comparisons takes place play multiple distinct roles but supposedly always \enquote{stay same}.We illustrate statement with simple Java example, \enquote{usual} languages, back it up $\lambda$-calculus existing implementations languages well.