Transverse translation-diverse phase retrieval (TTDPR), a ptychographic wavefront-sensing technique, is a viable method for optical surface metrology due to its relatively simple hardware requirements, flexibility, and high demonstrated accuracy in other fields. In TTDPR, a subaperture illumination pattern is scanned across an optic under test, and the reflected intensity is gathered on an array detector near focus. A nonlinear optimization algorithm is used to reconstruct the wavefront aberration at the test surface, from which we can solve for surface error, using intensity patterns from multiple scan positions. TTDPR is an advantageous method for aspheric and freeform metrology, because measurements can be performed without null optics. We report on a sensitivity analysis of TTDPR using simulations of a freeform concave mirror measurement. Simulations were performed to test TTDPR algorithmic performance as a function of various parameters, including detector SNR and position uncertainty of the illumination.