How do they test the low fluid level light during the IVA?

I've taken a couple of cars through the IVA test, one of the testers took the reservoir cap of the master cylinder to check the level switch activated the warning lamp. I didn't notice how the tester did this on my last test.

My brake fluid reservoir has a push button on the top.

They just pushed that on my SVA test.

Sure it's ignition on and handbrake off then test the cap if it's not got a button on then I guess they'll unscrew it and turn it upside down

Thanks, and how should this work with twin reservoirs, either reservoir can activate the switch?

I have a feeling the previous owner hasn't wired it up correctly and both reservoirs need to be pressed or low at the same time for the light to come on.

Yes, I'd go for either cylinder to light up the warning

Thanks,

Has anyone got a basic wire diagram?

It's simple wiring,the bulb has an ignition live to the positive side, then any switches you have go in the earth circuit.