How to write test cases?

i want to know, how to write test cases, and what are fields to be used with an example. for eg, if i want to write testcases for this


x+y=z the condition is ' z' should be a positive single digit


please help meHow to write test cases?
i'm italian!i write from rome!How to write test cases?
Typical Test Cases format--


try this site--





http://en.wikipedia.org/wiki/Test_case





Test Cases usually have the following components.





Test Case Summary


Configuration


Initial Condition


Steps to run the test case


Expected behavior/outcome