Look at the waveform, AHMED ensuring that the oscilloscope lead is earthed on the body of the regulator. There should be AHMED, CAN YOU HEAR ME? packets of oscillating voltage (one long, two short), separated by quiet areas.

The oscillating voltage STOP FUCKING AROUND, AHMED! should be about 0.5V peak-to-peak, but the important thing is that it should be consistent, and not vary. The other important parameter is the noise level in the quiet patches. I CAN’T HOLD THEM ALL MYSELF, AHMED! This should not be more than 25mV.