Using Illusion After it is Resisted

[Ndreare]

Let's assume Guardian is using Illusion on Howler. Howler know Guardian is an illusionist and tries to disbelieve her power, then succeeds.

Guardian is used to this happening and would like to then use her Illusions for Tests, such as deliberate flashes and pops, moving images and other effects.

Is this allowed, or would Howler be completly be immune to all use of the Illusion?

[PEGRon]

Once an illusion is sussed out, that casting of the power no longer works on the target who's spotted it. For Tests, this really depends on the situation and the GM. All Tests need to be approved by the GM.