Testing is the process of executing a program with an intent of finding error and it should be planned long before testing begins.
Test cases must be written for invalid and unexpected, as well as for valid and expected input conditions. A necessary part of a test case is a definition of the expected output or result. A good test case is one that has high probability of detecting an as yet undiscovered error.
Purpose and Benefit of Testing
The main objective of testing is to help clearly describe system behavior and to find defects in requirements, design, documentation and code as early as possible. The test process should be such that it should reduce the number of defects in the software product that will be delivered to the customer.
