7 Software Testing Principles Every Software Tester Should Know

7 Software Testing Principles

The objective of software testing is to ensure that the optimum checking is done while maintaining the final goal. The biggest challenge is, therefore, to ensure that the tester is following the right strategy.  It requires fixing some ground rules for the game.

For the benefit of our readers, we have given here seven basic software testing principles typically preferred in the software industry.

It can be best understood using a case study. Let us assume that you have to move a file from folder X to folder Y. Let us think of all the possible methods by which you can test this. Besides standard scenarios, one can also check for the following conditions:

  1. Moving file when it is still open.
  2. The user does not have the security rights to do any action in folder Y.
  3. The folder Y is operated on a shared drive, and it has no remaining storage capacity.
  4. There is another file with the same name in folder Y.
Software Testing Principles

We can go on and on, with so many other possible scenarios. To get a feel of the complexity let us assume that you have 20 input fields to be tested and each has ten possible values. This will make the possible combinations equal to 10^20.

Quite complex!! As the time and cost of testing will be quite high with such large no of possible combinations. But do not worry as you can make life simple by using the following tips.

Let us go through the seven principles that will be of great help in real life software testing situations:

Software testing Principles

1 Avoid Exhaustive Testing

As comprehensive testing will require substantial time and resources, so one needs to go for the optimal testing in line with the risk assessment.

2 Checking for Defect Clustering

For defect clustering, we use the Pareto’s law, which is 80% of the defects shall be found in 20% of the modules under testing. An experienced software tester can tell which modules to check for. But, be careful because if the same tests are done repeatedly on certain modules, then you will not be able to find new issues.

3 Use the Pesticide Paradox

You must be aware of the fact that when the same pesticides are repeatedly used against certain insects, they will eventually develop resistance against the pesticides thereby making them ineffective.

Similarly, if the same tests are done on specific software repeatedly, they will not be able to identify new issues. The testers will have to devise new testing methods instead of using the same techniques again and again.

The hard truth is that even after all the precautions, it is not possible to say with authority that now there will not be any issues. Do you remember, that even a company like Microsoft had faced issues during the public launch of their software?

But this is the reality and is true for all, and with experience one can improve performance.

4 Testing identifies defects

When you are testing a software using specific methods, it establishes the presence of certain defects. It is not possible to confirm the presence of no defects. Testing reduces the possibility of undiscovered defects, and one must accept that getting no defects does not mean to have the same results in all scenarios. At max one can say that the software is 99% bug-free.

5 The concept of “Absence of Error”

The software should be tested for the right requirement is more important than even the testing part. Otherwise, a software that is 99% bug-free may not perform in the required environment.

The software should be designed as per the user needs; else, your absence of error conclusion will prove to be an error of judgment. So, while testing software, it is a good idea to give careful thought about the actual user requirements and identify issues on this front.

6 The Principle of Early Testing

The software testing and development are best-done parallel. It helps to capture the issues related to conformity to user requirement and design errors at the beginning itself. It is also easy to do this in the initial stages. In our opinion, the testing should start as soon as the user requirements are defined.

7 Testing depends on context

The testing methods depend on the context in which it is to be used. The testing for an e-commerce platform will be different from the testing of an off-the-shelf commercial application. All software, even for the same application, are not identical.

They can be different in techniques, and it will affect the testing methods that need to be deployed for the specific purpose. For example, testing software for an online platform will be different from the testing software for a physical store.


To summarize the seven software testing principles highlighted above for trouble-free and effective software testing are:

  • Testing only identifies defects of the chosen context.
  • It is not possible to do 100% testing.
  • It is good to start the software testing during early stages of development.
  • Use the Pareto’s Law for defect clustering.
  • Be aware of the Pesticide Paradox while testing and avoid using the same methods at different stages.
  • The testing context should be in line with the final user requirements to be effective.
  • It is not a good idea to test the software just for nil errors.

Stating the principles is ok, but they are of no use if you forget to use them at the right time. The problem will not be solved only by learning the rules of the game, but as an experienced tester, one must thoroughly understand the rules and apply them naturally without any particular thought. Only then, they will be any help for you while doing software testing.

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