TESTING BASED ON ERROR GUESSING NERINGA SIPAVIČIEN Ė IFM-2/4 It is not actually guessing. Good testers do not guess…

THE PSYCHOLOGY OF TESTING Identifying failures during testing may be perceived as criticism against the product and against the author. Testing is, therefore, often seen as a destructive activity, even though it is very constructive in the management of product risks. Looking for failures in a system requires curiosity, professional pessimism, a critical eye, attention to detail, good communication with development peers, and experience on which to base error guessing. 2Testing based on error guessing

ISTQB GLOSSARY ERROR GUESSING - A test design technique where the experience of the tester is used to anticipate what defects might be present in the component or system under test as a result of errors made, and to design tests specifically to expose them. 3Testing based on error guessing

ERROR GUESSING (1) Perhaps the most widely practiced technique. Tests are derived from the tester’s skill and intuition and their experience with similar applications and technologies. When used to augment systematic techniques, intuitive testing can be useful to identify special tests not easily captured by formal techniques, especially when applied after more formal approaches. 4Testing based on error guessing

ERROR GUESSING (2) However, this technique may yield widely varying degrees of effectiveness, depending on the testers’ experience. A structured approach to the error guessing technique is to enumerate a list of possible errors and to design tests that attack these errors. These defect and failure lists can be built based on experience, available defect and failure data, and from common knowledge about why software fails. Error guessing has no rules for testing, it only uses the tester‘s previous skills. 5Testing based on error guessing

GRAY-BOX Notice that this is what might be called a „gray-box“ test because it requires the tester to have some idea about: typical programming mistakes, how those mistakes become bugs, how those bugs manifest themselves as failures, and how we can force failures to happen. 6Testing based on error guessing

EXAMPLES (1) Date field what the tester think for 30 and 31 date entry, but with having an experience of 5-10 years they get have an intuitions and guess a date for 29 Feb. Division by zero. Submitting a form without entering values. Entering wrong data in the fields and checking software behavior. Entering invalid values (alphabets for digits and vice-versa). 7Testing based on error guessing

EXAMPLES (2) and dot(.) in ids (eg: Ignoring the default maximum and minimum characters to be entered in some fields (that is entering values greater than or less than the expected values). For event driven applications, test multiple processes concurrently. Test using data created through the system or real records, because programmers tend to create data that reflects what they are expecting.... 8Testing based on error guessing

ADVANTAGES Highly successful testers are very effective at quickly evaluating a program and running an attack that exposes defects. Can be used to complement other testing approaches (equivalence partitioning and boundary value analysis). It is more a skill then a technique that is well worth cultivating. It can make testing much more effective. 9Testing based on error guessing

DISADVANTAGES Depends on testers experience: Knowledge of the application under test (AUT); Knowledge of the related testing types done (to understand where defects were found during the test); Knowledge of the integrating applications with their behaviour of response; Knowledge of typical implementation errors (such as division by zero errors); Experience of testing similar or related systems (and knowing where defects have arisen previously in those systems). Can’t be used as only testing method. 10Testing based on error guessing

QUESTIONS 1.What is error guessing? 2.Why error guessing might be called a „gray-box“ test? 3.What are the examples for error guessing? 4.What are rules for error guessing? 5.What are the advantages for error guessing? 11Testing based on error guessing

THANK YOU! 12Testing based on error guessing

REFERENCES Rex Black „Advanced Software Testing Vol. 1“ ISTQB Glossary ISTQB Foundation Level Syllabus Ivan Stanchev, Teleric Academy 13Testing based on error guessing