quote:Why do we write test cases?

As a tester, much of my work is writing test cases and executing test case. But when I think the following questions, I am still confused:
(1)Why do we write test cases? Is this is a good way?
(2)What is a good test case?
(3)How to execute test cases efficiently?

Why do we write test cases?
(1) To make testing be a manageable activity.
It can provide good evidence when boss and client check the testing status.
(2) To validate the testing coverage of application. It's very good for regression testing
(3) It can record what tester understand the system functionality. Then if any new man come for testing, he can execute the test cases by reading step by step. This can ensure that everyone can do this testing.