Introduction

Software testing is performed to verify that the completed software package functions according to the expectations defined by the requirements/specifications. The overall objective to not to find every software bug that exists, but to uncover situations that could negatively impact the customer, usability, and/or maintainability.

Testing is a process used to help identify the correctness, completeness and quality of developed computer software. With that in mind, testing can never completely establish the correctness of computer software. 

Software testing is the set of activities with the intent of finding the errors.

Software testing is an activity performed on the software during developing and after developing stage with the intent of finding the bugs and errors.

Important term:
Test Case:A test case in software engineering is a set of conditions or variables under which a tester will determine whether an application or software system is working correctly or not
 A good test case

is one that has a high probability of finding an as yet undiscovered error.A successful test is one that uncovers an as yet undiscovered error.