7 Principles of Software Testing: Learn With Examples

Jeffery Thompson
Innovative Leader in Custom Software Solutions: Jeffery Thompson, Founder of BIT Studios
Quality Assurance (QA)
12 min read
Published: Nov 1, 2022
Updated: Apr 23, 2023
7 Principles of Software Testing: Learn with Examples

The software testing process evaluates the functionality of a software product. 

But it’s far from being an ordinary process. To be effective, it has to adhere to certain principles of software testing.

In this post, you’ll find out these software testing principles. Plus, you’ll learn about forms of testing, testing methods, testing approaches, and more!

Why Are Software Testing Principles Important?

Why are Software Testing Principles Important?

Do software testing principles and practices matter? Yes, they do. In this section, let’s look at the reasons you should take the principles of testing software to heart. 

They Ensure the Software Product Is Bug-Free

Bugs exist because there’s a gap between what a software program does and what the user expects to happen. Close this gap and you create a mostly bug-free software product

Software testing principles serve as your guide in doing that. They focus on detecting defects. The more bugs you identify, the more bug-free your software.

They Check if the Product Complies With Technical Specifications

Why are technical specifications important? For one, they can infuse consistency into the software project. 

Technical specs serve as a reliable reference point. And we’re not just talking about references for building the software. But also for setting performance metrics.

So why should you adhere to testing principles in software engineering? The answer is simple. It helps ensure you build a technically sound software product.

They Make Sure the Product Meets User Requirements

Yes, your software product can have many cool features. But if those features don’t meet user requirements, your product becomes useless.

This is where the principles of software testing come in. They always emphasize testing for usability. After all, it doesn’t matter how cool the features are. If they don’t meet user requirements, the software is unusable.

They Review the Product’s Functionality and Performance

When consumers use your software product, they expect it to function like it’s supposed to. 

Software testing principles call for functionality and non-functionality testing. The aim is the same for both, of course. And that’s to detect the presence of defects in the functionality. 

Sometimes the functionality is fine, but the performance leaves much to be desired. For instance, a button works, but it takes forever to load. Another example is when it takes longer to process, retrieve, or display data. 

One principle of software testing states that testing is context-dependent. So don’t test for functionality only. Make sure the performance also holds up.

You now know how important they are. So are you ready to learn about the principles of testing software? Okay, let’s do this!

Principles of Software Testing: Your Guide to the Testing Process

Principles of Software Testing: Your Guide to the Testing Process

There are seven principles of software testing. That sounds like a whole lot to be familiar with. 

But don’t you worry. We’ll dive into all the test principles in the succeeding sections.

1. Testing Shows the Presence of Defects

This principle explains the purpose of the testing process itself. And that is to show the presence of defects.

Note that it doesn’t say “aim for the absence of defects.” That is something that the software development team can aim for.

But it’s a different story with test teams. Their job is to look for bugs. And it’s always preferable to detect and resolve bugs before the deployment stage. 

Still, allow us to mention something that’s vital. Despite your best testing efforts, you can’t guarantee software that’s 100% error-free. It is true to the testing process as it is to the software development life cycle (SDLC). 

Sure, you might be able to fix every defect you discover during testing. Even then, it’s no guarantee that your software is bug-free.

Of course, you can use various methods to ensure your software product is as bug-free as possible. 

For instance, regression testing does a fine job of making sure the code remains intact. Even if there’s a code change, you can check if the existing functionality still works.

Unfortunately, defects may still appear after the testing process. Apps may exhibit bugs after getting deployed in the environment. Software programs may have errors after end-users have started using them. 

To summarize this principle:

  • The testing process’ goal is to find defects. It’s not aiming for the absence of defects.
  • It doesn’t guarantee a 100% bug-free software product.
  • A software program may still exhibit bugs even if you resolve its defects during testing.

2. Exhaustive Testing Is Impossible

There’s no harm in trying to uncover all kinds of defects. Exhaustive testing, however, simply can’t detect all possible bugs in a software product.

But wait — what exactly is exhaustive testing? It involves verifying all functionality in a software program. You do this by using valid and invalid inputs. For good measure, you also have to cover every pre-condition.

That sounds like a lot of work. Well, IT IS a LOT of work. 

It is tantamount to testing for every conceivable scenario. There is an infinite number of input and output combinations. And that just applies to test cases you’ve come up with. It doesn’t account for every situation the end-user will face using your software.

Besides, exhaustive testing is not always practical. Theoretically, you can attempt it. 

But it’s a different story in the real world. Remember that each test case you test expends resources. We’re not only talking about time but money as well. 

This is why test planning is key. You should always devise a testing strategy. It should help you set limits on your testing process. You can identify areas to focus on. This way, you can avoid never-ending testing.

To recap exhaustive testing:

  • Exhaustive testing is not possible in real-world situations. You can’t test for all possible user scenarios.
  • Testing costs time and money. You don’t have infinite resources to do never-ending testing.
  • Test planning is vital. It lets you identify areas to focus on when testing.

3. Early Testing

How early should you start the software testing process? It might be earlier than you expect. In fact, you should begin as early as possible. Yes, even in the early phases of the software development life cycle (SDLC).

This software testing principle states that it’s never too soon to do early testing. Logic dictates that you do tests after coding has begun. But you can actually perform early testing even before the development stage.

So when do early testing testers start doing their jobs? They can do it as early as the requirements-gathering phase. They can test each requirement, even if it just involves a feasibility analysis.

Can early testing make a difference? The answer is yes. It makes a world of difference.

Let’s go back to the previous example. What happens when you test the requirements early? For one, you can spot and fix issues before they can cause you any trouble. And when we say trouble, we mean cost overruns and delays. You might end up not finishing your software project on time and within budget.

Moreover, some issues might have a domino effect. There’s no telling how they can affect other functionalities. The cost to fix everything could derail your project.

So let’s sum up:

  • Early testing could mean testing as early as you can. Even before coding begins, you can perform early testing.
  • The earlier you can detect issues, the better. Fixing issues before development starts is cheaper than doing it after development.

4. Defect Clustering

What does defect clustering mean? It’s a situation wherein a particular module has the most bugs or errors.

What can cause defects to cluster? It has something to do with the nature of certain defects. There are just bugs and errors that tend to cause more issues. 

Say, your module has conditions in its code. And then there’s a variable there that’s erroneous. Odds are, it will affect other parts of the code. The most vulnerable are those directly dependent upon that variable.

There’s this thing called the Pareto Principle in software testing. It states that 80% of errors come from 20% of the modules. Meanwhile, the remaining 20% of those issues come from the remaining 80% of the modules. 

The Pareto Principle is defect clustering in action. The majority (80%) of the issues originate only from a minority (20%) of the modules. So somewhere within those few modules, defects are clustering like ants. Those few modules should be the top priority when testing.

Can a software tester pinpoint where defect clustering might happen? Yes, they can. If they’ve been testing software for many years, they should be able to tell. Their experience might help them spot which modules are high-risk from the get-go. Advanced testing skills might also allow them to identify likely defect clusters.

Time for a run-through:

  • Defect clustering happens when issues pile up in a particular module. 
  • The Pareto Principle in software testing is defect clustering in action.
  • When testing, focus on high-risk modules that are likely to have defect clusters.

5. Pesticide Paradox

Wait — are we talking about pesticides in a blog post about software testing? 

Yes, we are, and with good reason. So let’s get right to the explanation. 

Testing teams often refer to the Pesticide Paradox when testing software. So what exactly is the Pesticide Paradox? It is the practice of using the same test cases again and again. Over time, these test cases will no longer detect new defects. So even if you’re using legit test cases, they might not work in future testing processes.

What’s that got to do with pesticides? Well, there’s this theory about using pesticides to get rid of pests. According to this theory, you can’t spray the same pesticide over and over again. The reason is that the pests will develop immunity over time. Sure, the pesticide might have worked before. But in the next applications, it has become useless.

Can you avoid becoming a victim of the Pesticide Paradox? Well, we have some good news for you. The answer is quite simple. You need only review and update your existing test cases regularly. Never use the same tests again.

Let’s summarize:

  • Beware of the Pesticide Paradox. Don’t use the same test cases again and again.
  • Update your existing test cases regularly. They might have worked the first time. But you need to improve them always.

6. Testing Is Context-Dependent

What does context-dependent testing mean? It means that testing processes can vary depending on the software’s specific context.

You can get an idea of the software’s context through its project requirements. Of course, each software project has its own set of requirements. Testing should align with those unique requirements. 

Again, we go back to the subject of test cases. To develop them, you base them on the user requirements. After developing such test cases, you execute them during the testing process.

You can follow sound principles of test case design in software testing. One is that test cases should be simple. Also, they should be specific. In other words, you design a test case to look for a specific error. Don’t design a test case for the entire functionality, and hope it detects errors. 

To summarize: 

  • Testing varies depending on the software’s context. The project requirements should tell you more about its context.
  • Leverage test cases to detect specific errors. The more specific the test case, the better.

7. Absence of Errors Fallacy

Is a defect-free or error-free software product a good product? Not always. Allow us to explain.

True, a software product can pass the testing process. In other words, it appears to have no bugs or issues. But having zero errors doesn’t mean it fulfills the user requirements. 

Let’s do a basic example. Say you’re building a software program that generates expense reports. It has the features to do its job. Every button works, and every page loads. But the user has to navigate through 15 steps to create a simple report. And the file export options are really limited. And is that a letter O or a zero?

Sure, it has no defects. But is it usable software? 

Let’s recap the absence of errors fallacy:

  • An error-free software product does not make a good software product.
  • If a software product does not fulfill user requirements, it is unusable software. 


The 7 principles of software testing exist for a reason. They’re there to guide you in executing an effective testing process

Understanding software testing principles also offers other benefits. They can help you build a better testing approach. You can manage your software testing team better via these fundamental testing principles.

Do you want to learn more about the principles of software testing? Contact us today and we’ll be happy to help you.

Originally published November 1, 2022, updated April 23, 2023

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