  Since its discovery, differential linear logic (DLL) inspired numerous
domains. In denotational semantics, categorical models of DLL are now commune,
and the simplest one is Rel, the category of sets and relations. In proof
theory this naturally gave birth to differential proof nets that are full and
complete for DLL. In turn, these tools can naturally be translated to their
intuitionistic counterpart. By taking the co-Kleisly category associated to the
! comonad, Rel becomes MRel, a model of the \Lcalcul that contains a notion of
differentiation. Proof nets can be used naturally to extend the \Lcalcul into
the lambda calculus with resources, a calculus that contains notions of
linearity and differentiations. Of course MRel is a model of the \Lcalcul with
resources, and it has been proved adequate, but is it fully abstract? That was
a strong conjecture of Bucciarelli, Carraro, Ehrhard and Manzonetto. However,
in this paper we exhibit a counter-example. Moreover, to give more intuition on
the essence of the counter-example and to look for more generality, we will use
an extension of the resource \Lcalcul also introduced by Bucciarelli et al for
which $\Minf$ is fully abstract, the tests.
