Rspec

How i can write spec for already existing model??? i need to write the
test cases for already existing model…

The same way you would for a model you don't have.

Look at the model, and identify all that it does, then write tests to
ensure that does all you assume it to do (and not do)

Andrew Timberlake
http://ramblingsonrails.com
http://www.linkedin.com/in/andrewtimberlake

"I have never let my schooling interfere with my education" - Mark Twain