power off, disconnect motor and check coils conductivity(hold two ends of coil together - rotor is very hard to rotate, same with other two wires, but not so hard if all 4 wires together), connect back to driver;
check power of driver, motor rotor should be holded with some force when powered and loose if power off;
connect step- to arduino GND, powers arduino, connect and disconnect step+ to 5V periodically (or little battery between step + and - )