Topic: How I can use unit testing?

Hello Folks,

I am new to rails and I have finished from my project , but I do not know how I can test it using unit testing. I tested every method and class in my application and I have fixed my issue in my code, but do you think I need unit testing?

I google it and I read some articles about it but still not very clear to me, because some people said use Test::Unit ,but I found it need to write a code for this test and I am not expert in rails.

Is there anyway to test my application automated?