How could i make Autofill forms bot for a external website which is using StepForm

i need to make a test for an anti-spam system for a website. I had consulted this topics:

About first link i found that i cant do this from external host , and need to make a browser extension. In second link code is using submit.php but that form dont have any scripts on hosts to submit this. In 3th link code works with iframe on the host. In the last link its about python and i have tried to search more about autofill bot in python. I dont get any success in it. What i need?: I have a site what is using StepForm module for form, i need to make a bot for autofill it to test anti-spam plugin. How could i make it?

Thx for any help.