Driving a stepper motor using ESP8266
I hope there must be an inbuilt pull-up resistance for each GPIO registers of ESP.

Test like this and post your observation:
 1. Don't connect anything(ULN2003 jumper wires) to your ESP and check the GPIOs you selected whether they are floating or not. If no float in reading then it's fine.
 2. Connect the load and test the GPIOs are floating or not.