  We apply the joint lensing and dynamics code for the analysis of early-type
galaxies, CAULDRON, to a rotating N-body stellar system with dark matter halo
which significantly violates the two major assumptions of the method, i.e.
axial symmetry supported by a two-integral distribution function. The goal is
to study how CAULDRON performs in an extreme case, and to determine which
galaxy properties can still be robustly recovered. Three data sets,
corresponding to orthogonal lines of sight, are generated from the N-body
system and analysed with the identical procedure followed in the study of real
lens galaxies, adopting an axisymmetric power-law total density distribution.
We find that several global properties of the N-body system are recovered with
remarkable accuracy, despite the fact that the adopted power-law model is too
simple to account for the lack of symmetry of the true density distribution. In
particular, the logarithmic slope of the total density distribution is robustly
recovered to within less than 10 per cent (with the exception of the
ill-constrained very inner regions), the inferred angle-averaged radial profile
of the total mass closely follows the true distribution, and the dark matter
fraction of the system (inside the effective radius) is correctly determined
within ~ 10 per cent of the total mass. Unless the line of sight direction is
almost parallel to the total angular momentum vector of the system, reliably
recovered quantities also include the angular momentum, the V/sigma ratio, and
the anisotropy parameter delta. We conclude that the CAULDRON code can be
safely and effectively applied to real early-type lens galaxies, providing
reliable information also for systems that depart significantly from the
method's assumptions.
