(* Equivalence is false: r(a,b) fails, a succeeds *)

free c, a, b.

reduc r(x,x) = x.

process
        let y = choice[r(a,b),a] in out(c,y)

(* EXPECTPV
RESULT Observational equivalence cannot be proved.
0.008s (user 0.000s + system 0.008s), max rss 7300K
END *)
