Explaining about Test Cases and Types?

Test Cases:

 - Test case is a set of pre-conditions,test scripts,input data and expected result to validate functionality of system.

OR

 - Test case is a brief description of what to test and how to test in application.

Types of Test-Cases:

 1.Positive Test-case:

    - If test case is prepared to check what system supports to do,then it's called positive test case.

ex: Check login with valid inputs.

 2.Negative Test-case:

    - If test case is prepared to check what system not supports to do then it's called negative test case.

ex: check login with invalid inputs.

- while preparing test-cases,Every tester can follow IEEE A29 format.