how to find out wether the stepper motor is working or not?
First, make sure all the connections have continuity.  If the motor has 6 wires, then it's probably two pairs of coils with a common wire for each pair.  Use a ohmmeter to find which wire of each group of three is the common, and connect those wires to the positive supply.  Then manually connect one of the remaining 4 wires to ground in sequence.  You should see the motor jump a little each time you change wires.

If that works, the motor itself if OK and the circuit is the problem.  If that doesn't work, then we need to know a lot more about the motor.  Report on the result of the above and this answer can be expanded.  A link to the motor datasheet would of course also help.