Checking stator

[steplift20]

150 1988 Mercury out board, I had a problem with my engine and I am going to change my 2 switch boxes but I want to check my stator, my question is this, I have the batterys out of the boat do I have to install my battery to do the test? I know it has to be grounded to the engine and turned off but do I have to put the batterys in. Can it be tested with the batterys out.