  When a photon collides with a laser pulse, an electron-positron pair can be
produced via the nonlinear Breit-Wheeler process. A simulation framework has
been developed to calculate this process, which is based on a ponderomotive
approach that includes strong-field quantum electrodynamical effects via the
locally monochromatic approximation (LMA). Here we compare simulation
predictions for a variety of observables, in different physical regimes, with
numerical evaluation of exact analytical results from theory. For the case of a
focussed laser background, we also compare simulation with a high-energy theory
approximation. These comparisons are used to quantify the accuracy of the
simulation approach in calculating harmonic structure, which appears in the
lightfront momentum and angular spectra of outgoing particles, and the
transition from multi-photon to all-order pair creation. Calculation of the
total yield of pairs over a range of intensity parameters is also used to
assess the accuracy of the locally constant field approximation (LCFA).
