All,
During an interview with an major MNC , I was asked this curious question of " What is meant by pesticide paradox ? " I have been working as Test Engineer for almost 4 Years but I have never came across this terminology.
Can some one help me with a real time example ?
Pesticide Paradox
The phenomenon that the more you test software, the more immune it becomes to your tests - just as insects eventually build up resistance and the pesticide no longer works. [Beizer]
from: https://strazzere.blogspot.com/p/testing-terms-glossary.html
Lets say you are testing an application. You have written a set of test cases.
Now you run one cycle of testing. You find few bugs and report them to the development team. Development team fixes the bugs and reverts to you with the updated code. You again execute the same set of test cases. This time you find that few of the bug were still not fixed and you report that back to the development team. They work on it and send an update to you. Once again, you execute the same set of test cases and don't find any bugs.
Now in a new release some changes were made in the application. You run the same set of test cases and they all pass. But, what you miss here is the new bugs that may have introduced when the fix and new changes were applied. The old set of test cases are incapable of identifying these new bugs.
This is called Pesticide Paradox. To avoid this you need to update your test cases with each cycle and add new cases to the old set.
Boris Beizer wrote “Every method you use to prevent or find bugs leaves a residue of subtler bugs against which those methods are ineffectual.”
In the most simple terms not every method or technique will find or prevent all bugs, so we must use a variety of approaches, techniques, and methods in testing.
Pesticide paradox can be also explained as: If the same tests are repeated over and over again, eventually the same set of test cases will no longer find any new bugs. To overcome this 'pesticide paradox', the test cases need to be regularly reviewed and revised, and new and different tests need to be written to exercise different parts of the software or system to potentially find more defects.
As defined on ISTQB Syllabus:
Pesticide paradox: If the same tests are repeated over and over again, eventually the same set of test cases will no longer find any new defects. To overcome this “pesticide paradox”, test cases need to be regularly reviewed and revised, and new and different tests need to be written to exercise different parts of the software or system to find potentially more defects.
So when a software is a subject of continuous changes and updating repeating the same test steps and scenario will make the software undiscovered bugs immune against the testing. That is why to avoid "Pesticide paradox" keep your test cases uptodate when ever a change or fix is applied on the testing area and always try to add new test scenarios and steps whenever possible. Also have different tester check different areas on each regression or release.
if test plan was followed a standard/requirement to define, when all set of the test cases were passed after bugs fixed, I don't see Pesticide Paradox is right! if our target is to ensure the DUT/SUT compliance with the standard or customer requirement, we should run same set of the test plan to ensure no regression happen and no new test plan should be added until new requirement added.
The pesticide paradox is not a paradox at all, and whoever invented the term was probably just trying to make money from it. It is not an intrinsic problem of the tests themselves, rather a symptom that your test function is inadequate. The concept behind the fancy name is more commonly referred to as code coverage. i.e. its no good having 1000 tests that all pass if they only exercise 1% of your code base. This is why some metric of code coverage is critical to a good quality assurance function. It's common sense really.
When the same kinds of tests are repeated again and again, eventually the same set of test cases will no longer be able to find any new bugs.
To overcome this “Pesticide Paradox”, it is really very important to review the test cases regularly and new and different tests need to be written to exercise different parts of the software or system to potentially find more defects.
