  Normal-mode coupling is a helioseismic technique that uses measurements of
mode eigenfunctions to infer the interior structure of the Sun. This technique
has led to insights into the evolution and structure of toroidal flows in the
solar interior. Here, we validate an inversion algorithm for normal-mode
coupling by generating synthetic seismic measurements associated with input
flows and comparing the input and inverted velocities. We study four different
cases of input toroidal flows and compute synthetics that take into account the
partial visibility of the Sun. We invert the synthetics using Subtractive
Optimally Localized Averages (SOLA) and also try to mitigate the systematics of
mode leakage. We demonstrate that, ultimately, inversions are only as good as
the model we assume for the correlation between flow velocities.
