It appears that negative testing is sometimes ignored. Some managers decide to execute negative tests at the late phases of the development process, before acceptance testing.
In this case correction of the detected defects may take much more time than anticipated, and the project will likely miss the deadline.
Specialists in manual and automated testing recommend including negative tests in any testing type, in particular in functional testing. It is good if about 20 % of the test cases are negative, such amount of negative tests is usually sufficient for revealing defects that can turn into serious problems after the application release.
Common Negative Tests Are:
- entering more or fewer than required characters in the field;
- typing letters in the field where numeric data should be;
- entering various specific characters and characters from other languages;
- trying to logging into one account from different devices or browsers simultaneously;
- interrupting data processing at different stages;
- attaching files that are larger than assumed in the requirements;
- sending and receiving files that are larger than assumed in the requirements and so on.
So, one shouldn’t forget about negative test cases planning web site testing, desktop testing and mobile application testing. They are a useful instrument for finding serious unexpected errors.