Here is a simple way to prove out the starter, battery and the main high current wiring.
Take a wire with spade connector and connect it to the spade lug on the solenoid, don't turn the key on (unless you need it to start)
touch the other end of the wire to battery positive. This will bypass all the bikes secondary wiring to pull the solenoid in and energize the starter.
If the bike cranks over you have eliminated the battery, starter and all the main connections.
If it fails to crank of course you have other problems.
If you have a Voltmeter across the battery you will read around 10 Volts while cranking.
CAUTION, make sure you are in neutral or it could launch, pull the clutch in for extra safety.
This is the method I use when doing a compression test, it spins the engine over without adding fuel or spark, as the key is off the coils, pump and injectors are not operating.
Of course if its a bike with carbs you still get fuel because you have the throttle wide open.
The other day a local store had digital battery load testers on sale so I picked one up, this puts a load of 125 Amps on the battery and allows you to enter the Cold Cranking Amps from 200 to 1,000 Amps
I found all my bike batteries would pass on the 200 range but not 300, the default is 500 Amps for a car battery. Of course a bike battery will fail if you forget to change the CCA setting but no harm done.
It doesn't actually change the current when you set CCA but it uses the number in a calculation to assess the health.