How to non-destructively test unknown LED strip?
I would use a 5V power supply with maybe a 1 k&Omega; resistor in series and start probing pairs of pins.  The smallest likely forward drop accross a LED is 1.8V, which would put a bit over 3 mA thru it.  Neither 5 V nor 3 mA should damage the LEDs, but that should be enough current to see them light up if you're doing this in normal office lighting.