I think that it's only the fluid level light that is required. Operation of the same light by the handbrake is actually just a simple way of proving that the bulb hasn't blown.
I put a kit-car through the SVA and the requirement was for a fluid level warning light and a method of testing it (later revised to a method of testing it from the drivers position). A simple test pushbutton on the dash or a timer linked to the ignition would both satisfy the requirements. Before the position change, the push-to-test top on the brake reservoir of some cars was sufficient.
SteveW