Testing circuit with directional coupler. A testing circuit can include a testing circuit input configured to receive an output signal from a module, the output signal having a fundamental component and a harmonic component. The testing circuit can further include a testing circuit fundamental output configured to output the fundamental component and a testing circuit harmonic output configured to output the harmonic component. The testing circuit can include a first directional coupler having a first coupler input coupled to the testing circuit input, a first transmitted output coupled to the testing circuit fundamental output, and a first coupled output coupled to the testing circuit harmonic output.