The test uses a nested std::map of packet error ratio (PER) values that have been manually computed for a given MCS, size (in bytes) and SNR (in dB) in order to verify against the PER calculated by the model. The internal map has type `std::map<double, double>`. In converting this map's key type (SNR) from double to the nholthaus/units strong type (which converts from double), some tolerance issues were observed in std::map::find(), causing test failures. The solution is to check for keys by comparing them against the target value with an epsilon precision.