Known-answer PXRD test pattern: synthetic CuKa powder pattern of cubic perovskite SrTiO3 (Pm-3m, a=3.905 A) computed with pymatgen XRDCalculator, grid-sampled with Gaussian broadening (sig 0.03 A^-1), Q units from 0.5 to 8 A^-1. Ground truth: strongest peak (110) at q=2.277 A^-1. Useful as a control input for testing PXRD prediction routes.