Principles of Software Testing

Principles of Software Testing

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Software testing is an inseparable and inescapable part of software development. It lets you uncover any gaps, errors, and defects in a product and ensure it meets all the specified requirements. It is essential to carry out this process carefully with the best results to deliver high-quality software. This is where the role of the principles of software testing comes into play. 

These principles assist you throughout the testing process to ensure you follow the right strategy without deviating from your goal of producing defect-free software products to end users. 

In this blog post, we will discuss some essential principles of software testing every tester must follow. 

What is Software Testing? 

It is the process of executing different test cases against the specified requirements to check if a software product works as intended. It involves uncovering and fixing defects and bugs to ensure the delivery of high-quality, defect-free products. 

For example, consider you developed a social media application that prompts users to log in before using it. In this case, you need to test the application for different test cases, such as: 

  • Verify that a user can log in with a valid email address and password. 
  • Verify that a user cannot log in with either of the invalid email address and the password. 
  • Check that a user cannot log in with any of the blank fields – the email address and password. 
  • Verify the log-in button works correctly and takes users to the application. 
  • Check the ‘Forgot Password” link functions as intended.

Check out in detail about the test cases for the login page here

These are just a few test cases for a single page. There will be different test cases for each page and element of an application. This ensures that the final application released into the market is free from defects and functions as expected. 

While evaluating any software product, testers do the following: 

  • Verify that the product is free from bugs. 
  • Checks if it conforms with the technical requirements specified in the design stage. 
  • Ensure the product meets the client’s needs. 
  • Gauge the product’s performance and functionality. 
  • Look for different methods to improve its reliability, scalability, and usability.

During testing, the product (its various components and aspects) undergoes rigorous checks to identify any bugs or errors.  If they are found, the testing team reports them to the development team to get them fixed. 

The end goal is to deliver a product that is fully featured, reliable, secure, usable, free from defects, and meets all customer requirements. 

Check it out in detail about Software testing here

Why are Software Testing Principles Important? 

In our personal and professional lives, we follow certain ethics and rules to live better and get our things done properly. Whether achieving a work goal, staying fit, or other life goals, you must follow certain rules to accomplish your target. The same applies to software testing. 

Software testing principles are standards, rules, or guidelines defining how software testers should conduct testing effectively by managing the available resources, time, and budget. They help test engineers create reliable, defect-free, and maintainable code. Also, it becomes easy for the testing team to create an effective test strategy and craft error-catching test cases. 

Here are the benefits of adhering to the principles of testing: 

  • Reduce time and effort in the testing process. 
  • The entire development and testing teams follow the proper conventions and standards throughout an application’s life cycle, making it more maintainable.
  • Foster collaboration between developers, testers, and other stakeholders, resulting in improved communication and a better understanding of the product requirements.
  • Provide some estimated assumptions useful during testing, which can reduce a lot of time and effort.

7 Principles of Software Testing

1. Testing Shows the Presence of Defects

This testing principle states that software testing concerns the presence of defects, not their absence. It involves identifying bugs in the software product and fixing them before deploying and releasing it to the market. 

However, it is important to note that testing does not make the product defect-free 100%. Instead, it reduces the number of defects. Even repetitive testing and bug repair may leave some bugs unfound. 

This means your application may seem defect-free after several rounds of testing. But when you deploy it into the production stage, it is a possibility that unexpected errors can occur. As a result, the testing team should take care of this and make necessary efforts.

2. Exhaustive Testing is Impossible

Before shedding light on the principle, let us understand exhaustive testing. It tests and verifies every functionality of the application using both valid and invalid inputs. 

This principle states that it is not possible to test EVERYTHING. This is because the combinations of input and output are infinite. Hence, it is not possible to check your application for every combination. You just create some primary test cases according to your use cases, and if they pass, you need to assume that the application will work correctly. 

Even if you try to cover all possible input and output combinations, the amount of time, resources, and cost will increase. As a result, testing teams need to assess all potential risks and create test cases accordingly while ensuring they test the significant functionality of the application. 

3. Early Testing

This testing principle says that it is beneficial to start testing as early as possible in the software development life cycle (SDLC). In fact, validating requirements starts even before coding. This uncovers potential bugs and errors in the software design and prevents the cost required to fix them if they were found in the later stages of development. 

Early testing saves a lot of effort and time because resolving those issues in the later stages can become more complicated and critical and may require the team to rewrite some functionality. 

Consider two scenarios: the first, where you found errors in the requirements gathering and analysis phase, and the second, where you found errors in a fully-developed application. Think about both scenarios and determine which one is less expensive and requires less time. Obviously, the first scenario. 

More interestingly, early testing is one of the fundamental principles of Agile and considers an essential activity throughout the development rather than just a single phase, unlike the waterfall model.

4. Defect Clustering

Defect clustering refers to an application’s modules or features containing more bugs, generally resulting in operational failure. It is very less likely that bugs are distributed evenly throughout the application. Hence, testing should concentrate on such modules and features.  

Pareto Principle states that 80% of software issues come from 20% of modules. On the other hand, the remaining 20% of issues come from 80% of modules. Hence, focus on testing the 20% of modules that create 80% of issues. 

The most challenging part is how to determine the modules containing bugs. Well, this entirely depends on the team’s knowledge and experience.

5. Be Aware of Pesticide Paradox

When you spray pesticides on crops, insects get used to them and build immunity, making them ineffective to pesticides as time passes. When you repeat the same test cases repeatedly, they will stop finding new issues. 

To avoid the concept of the Pesticide Paradox, it is essential to review and update test cases regularly, in addition to improving the existing test methods or implementing new ones.

6. Testing is Context-Dependent

Every software is developed with a different purpose. Hence, testing depends on the context of the software. As different types of software have distinct requirements, they require different types of testing. The same tests cannot detect all the major flaws in different types of applications, as users might have different ways of interacting with the product. 

For instance, there are different types of cases for an E-Commerce application and a social media application. The same test cases on different products may not detect all the defects in one of the products.

7. Absence of Errors Fallacy

This principle states that it becomes unusable if your application is 99% bug-free but does not satisfy the end user’s requirements or business needs. There is a misconception among people that if you build 99% bug-free software, users will automatically use it. To make any software usable, it must satisfy users’ and business needs. So, run tests to check if the application meets the specified requirements.


This was all about the principles of software testing in software engineering. These principles are standards, guidelines, or rules every testing team must follow to ensure the proper execution of testing, resulting in high-quality software. Combining all these testing principles ensures an effective testing strategy that significantly saves time and effort, delivering high-quality software products.

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