Ruby Unit Testing, Need

I am fairly new to ruby application development and currently working on a small project where I have methods in Order and LineItem models to calculate sales figures. For instance: total_sales, total_cost, total_profit etc. Everything is working as it should. I need to perform unit testing for each of those methods mentioned above. I have tried googling but do not find it helpful. I would really appreciate if you guys would suggest some good resources where I can learn the syntax for Unit testing.