  The method-of-moments implementation of the electric-field integral equation
(EFIE) yields many code-verification challenges due to the various sources of
numerical error and their possible interactions. Matters are further
complicated by singular integrals, which arise from the presence of a Green's
function. To address these singular integrals, an approach was previously
presented wherein both the solution and Green's function are manufactured.
Because the arising equations are poorly conditioned, they are reformulated as
a set of constraints for an optimization problem that selects the solution
closest to the manufactured solution. In this paper, we demonstrate how, for
such practically singular systems of equations, computing the truncation error
by inserting the exact solution into the discretized equations cannot detect
certain orders of coding errors. On the other hand, the discretization error
from the optimal solution is a more sensitive metric that can detect orders
less than those of the expected convergence rate.
