Software development is the process of conceiving, specifying, designing, programming, documenting, testing, and bug fixing involved in creating and maintaining applications, frameworks, or other software components software testing is an activity to check whether the actual results match the expected results and to ensure that the software system is Defect free. Testing is a very important step in software development to ensure that the software does properly, what it is supposed to do. While the development of the software there arise certain problems that leads to error, defects, and complications in the software testing to make the software run smoothly. In this report, I tried to over whole software testing, why software testing is required, hoe test cased are made, types of testing, levels of testing, method of testing, why software testing, levels of testing, method of testing & further how important software testing is. In short, we can say that testing is the last step in the software development life cycle.