  The scale of small-field inflation cannot be constrained via primordial
gravitational waves through measurement of tensor-to-scalar ratio $r$. In this
study, I show that if cosmic strings are produced after symmetry breaking at
the end of hilltop supernatural inflation, this small-field inflation model can
be tested through the production of gravitational waves from cosmic strings.
Future experiments of gravitational wave detectors will determine or further
constrain the parameter space in the model.
