Causal Testing

We suggest an equivalence notion for event structures as a semantic model of concurrent systems. It combines the notion of testing (or failure) equivalence with respect to the timing of choices between dierent executions with a pre-cise account of causalities between action occurrences as in causal semantics. This lls an open gap in the lattice of equivalences considered in comparative concurrency semantics. We show that our notion coincides with a \canonical" equivalence obtained as the usual testing performed on causal trees. Further-more, we show that it is invariant under action renement, thus fullling a standard criterion for non-interleaving equivalences.