Linear diffusion test. Top: radiative energy profile at time t = 2 × 10^-13 for three calculations using α = 1 (black), α = 0.5 (red), and α = 0 (blue), i.e., using, respectively, Dirichlet, Robin, and Neumann boundary conditions at level interfaces. The analytical solution is represented by the dashed line. The right axis shows the AMR levels, i.e., the effective resolution profile (dotted line). Bottom: corresponding relative error as a function of the distance.