Test cases must be developed for valid and invalid input conditions


  • As we know that for better detection of defects we must need to develop test case for inavalid input conditions also

  • sometimes some test cases in some cases gives the correct execution for the invalid entries if that is the case our software quality must be decreased.

  • our software must work for the valid input conditions.


The probability of existing defects in a software component is directly proportional to the number of defects already detected in that software component.


  • We can say that a defect in some part of the software component may results in more defects in that software module or component.

  • if we test the software rigorously there might be chances of entering new defects.


Testing should be carried out by a team that is independent of the development group.


  • this principle is true for psychological as well as practical related reasons.

  • It is difficult to convince the developer that he/she to convenience that the software created by them is faulty.

  • and also they thought in the same way as they developed it so that it would be difficult to detect the defects.

  • so the developing team must be differ from the testing team.