Results of the R-type expansion test. Top panel: the value of the radius of the ionized bubble at the center of the simulation box, in units of the Strömgren radius R_St , plotted as a function of time (normalized by the recombination time t_rec). Different lines represent different resolutions 32³ (blue), 64³ (red), 128³ (green), 256³ (purple) with the orange, dashed line representing the analytical prediction given by Eq. (20). Bottom panel: the relative error |R(t) − R_r(t)| /R_r(t) between the analytical prediction R(t) and the numerical results R_r(t) as a function of t/t_rec.