How to know...

[Takumi86ES]

I would like to know how I know it is working.

[C0nw0nk]

http {
#nginx config settings etc
access_by_lua_file anti_ddos_challenge.lua;
#more config settings and some server stuff
}

If you have put it into your nginx config then you should see the Anti-DDoS Javascript puzzle. Unless you changed any settings / configurations in the script. (But Script as default will show the page instantly)