Test Case is a document which is prepare before the testing . Test case useful in Regression testing. 

Hi,
First of all I want to describe Test cases: “A test case has components that describes an input, action or event and an expected response, to determine if a feature of an application is working correctly.”

Fields in test cases:

Test case id
Unit to test: What to be verified?
Pre-Conditions
Test data: Variables and their values
Steps to be executed/Description of steps:
Expected result:
Actual result:
Result (Pass/Fail):
Remark/Comments: