Continuity check it to ensure you have wired it up right. Resistance check it for joint quality. I'd also do an insulation resistance check with a Megger between adjacent wires in the loom/pins in a plug.

Not sure if the pins you are using can be crimped, but I'd also crimp them rather than soldering them. Soldering is a shite idea for a loom that's subject to vibration! Also you open yourself up to stuff like dry joints and fecked insulation from soldering (hence it's important to check the loom!)