Sample of representing the test case:
Test Case # 1
Test Case Title: Testing the Post Issue mechanism
Preconditions: The userís PC is connected with the internet and user has browsed to the site of Railway Reservation & Information System.
Actions: Click Post Issue and issue form will appear.
User fills the Name and Email address fields.
User writes the issue in issue field and click Post.
If Name, Email address issue fields are empty system ask to fill these fields.
Expected Results: System should post the issue
Tested By: your name here
you must perform test case with each use case of your use case diagram.