Hi,

if you don't know anything about the language verilog, than start a very 
simple project. Try to describe a "OR", "AND", ... gate, several flip 
flops, counter, and so on. Write testbenches for all this simple tests. 
Than, and only than you can do this without problem and you feel save, 
take your module and start to write an testbench.

If you have no idea how to describe a OR gate, counter, etc. than begin 
to read literature, otherwise you will fail completely!!!

Regards

If you are new, why do you start with such a complex thing like a 
processor?
Start with an blinking LED, even there are enough pitfalls for a newbie.

in fact this "minimips" is vey interesting code!

My recommendation to qayyum salleh:
If you are new to the subject and want to learn Verilog hands on - start 
with some blinking LEDs, reaction on switches, some easy combinatorial 
logic and register logic examples.
If you want to continue towards more complex things - have a look at the 
website www.fpga4fun.com.
Another very good resource for learning purposes is the minimalistic 
MCPU at opencores (just google for MCPU...) I rewrote it from its 
functional specs and that helped me a lot to learn how things work ;)

Good Luck!