Testing begins during the first two satges of the software development process, this is because it will save money to fix problems earlier rather than wait until later making it less cost effective. Common errors that can happen during testing is bad time palnning, special cases(as in if you were doing a programme that does how many days are in a year you would have to think of leap year) and syntax errors. There are 3 types of test data
Normal Date: This should be tested to show that the program works as it was planned to. Examples of Normal Data could be the pass/fail program. Numbers like 20, 30, 80 etc.
Extreme Data: This is used to test the boundary limits within a programme. Again the pass/fail program is a good example of this the limits for that would be numbers lie 1, 49 or 51. Since the program is a pass if it’s more than 50 and a fail if it’s less than 50.
Exceptional Data: This is used to test that the program can handle unexpected inputs. Out of range date eg ABC, 1000 etc.
Tests are carried about by the development team but the Acceptance data is tested by the client. The alpha and beta tests are carried out by a select ban of users. For example the game Battlefield 3 is coming out this october and the company dice who develop it released an Alpha test back in early august for people to test and the beta is coming the end of this month for PS3, Xbox and PC users to participate in. This allows people to test it and report bugs and dice will be able to patch it in the final version. However doing all these tests guarantee that it will remove all the bugs. Battlefield 3 will still launch with a few bugs that will have to be fixed later on but all the major bugs will have been fixed while testing it the same goes for programmes.