Verification

• Constant solution $\uex = I$ ($V=0$) fulfills the ODE problem and the discrete equations. Ideal for debugging!
• Linear solution $\uex = Vt+I$ fulfills the ODE problem and the discrete equations.
• Quadratic solution $\uex = bt^2 + Vt + I$ fulfills the ODE problem and the discrete equations with linear damping, but not for quadratic damping. A special discrete source term can allow $\uex$ to also fulfill the discrete equations with quadratic damping.