can anyone tell my how to test one?

From 96 zrt600 servicing manual:

charge coil 1: 450.0 ohms between green and white wire on engine harness connected to cdi unit

charge coil 2: 25.7 ohms between green and black/red wire on engine harness connected to cdi unit.

Lighting coil: 0.21 ohms between two yellow wires on engine harness connected to main harness.

Timing sensor: 190 ohms between brown and green/wht wire on 2 wire connector on the engine connected to cdi unit.

good info RR see you on the river maybe the red!