better than a spark test: do a voltage drop reading........
Disconnect negative battery cable. Connect the red lead of an ANALOG voltmeter to the negative cable, the black lead to the negative terminal (on battery). Should read less than 2 volts, more if you have modern stereo with memory or clock, alarms,...
Sparking across a battery is always dangerous!
one more thing: Did you buy one of those cheap "lifetime warranty" crap alternators? ALWAYS buy a quality decent new or reman piece. Some remans are sent to Mexico for cleaning and Krylon and shipped back. Same goes for starters.
best of luck!
