If a circuit produced a perfect sine wave, there would be no harmonics ... video showing how he easily visualizes THD using LTSpice. Assuming you already have the system in question in LTSpice ...

If you click the probe inside V1 to measure current, you will see a sine wave going from -1 A to 1 A, just as you’d expect. Spice, LTSpice, and similar tools are an excellent way to experiment ...