How to know if test points can introduce EMC problems
A rule of thumb is start worrying when a stub length approaches 1/10th wavelength.
1GHz/3e9=333mm/10=33mm. PSU switchers are unlikely to have any significant harmonics at 1GHz so you should be OK. You will normally have more issues with common mode harmonics from 20-100MHz. Still, I usually refrain from putting test points on the actual switching node.