Have you ever wondered what software testing actually is?
When someone outside software engineering asks me this, I usually explain it something like this:
Everything that runs on a computer, smartphone, or other digital device is either software or controlled by software. Your operating system is software. Your browser is software. Every app on your smartphone is software.
All of this software has to be developed. And at some point, we need to find out whether it actually does what it is supposed to do – and how well it does it.
That is what software testing is all about.
Testing means examining software, questioning it, and trying it out. The aim is to find out where problems lie, what risks exist, and whether the product is good enough for its intended purpose.
That may sound simple at first. But professional testing involves much more than opening a finished application and clicking around a bit.
What Is Software Testing?
In short:
Software testing helps us understand how well software works, where problems lie, and what risks remain.
It is not just about finding obvious defects.
Testers ask questions such as:
- Does a function work as intended?
- What happens with unusual inputs?
- Is a requirement actually clear?
- How does the software behave when something goes wrong?
- Does it also work under realistic conditions?
- Which problems would be particularly critical for users?
Good software testing therefore often starts not with a click, but with a question.
Testers Do Not Automatically Improve Quality
A common misconception is that testing alone automatically makes software better.
If a tester finds a failure in the checkout process of an online shop, finding it does not fix it. What testing does provide, however, is information about quality and quality risks.
Based on this information, developers and product owners can decide how to address defects and improve quality in a targeted way.
And that is how testing can ultimately contribute to better products.
Why Is Software Testing Important?
Software testing is important because it can identify quality risks early and provide a reliable basis for decisions about whether software is ready for release.
Software can behave differently from what we expect in countless ways.
Take a simple example:
An online shop offers free shipping on orders of €50 or more.
At first glance, that sounds like a simple rule.
But what happens with:
- €49.99?
- exactly €50?
- a discount that brings the cart total back below €50?
- a voucher?
- a cancellation?
- a different currency?
Even one small feature can give rise to many different scenarios.
The job of a tester is not to try as many variations as possible at random.
It is about identifying the cases that are interesting and carry the greatest risk.
That is one of the key differences between “doing a bit of testing” and professional software testing.
Testing Does Not Start Only When the Software Is Finished
Another common assumption is this:
Developers build the software, then hand it over to a tester who looks for defects.
In practice, testing can start much earlier.
Imagine a requirement that says:
“The search function should return results quickly.”
What does “quickly” mean?
One second? Three seconds? Ten?
And how many products does the search cover? A hundred? A million?
Simply reading the requirement reveals that it is unclear.
We do not even need working software to spot that.
Testers can therefore help challenge requirements, uncover misunderstandings, and identify potential problems before they find their way into the product.
If you are interested in this aspect, you can find out more in our article “Five Reasons Why Requirements Engineering Is Important for Testers”.
Can Software Be Tested Completely?
In most cases, no.
Consider an application that runs on different browsers, smartphones, and operating systems. Then add different users, inputs, settings, and data. Imagine a form with just 10 checkboxes: that alone gives you 2^10 = 1,024 possible combinations. With a complex application, exhaustive testing is simply impossible.
That means testers have to make choices.
Which areas are particularly important?
Where is there the greatest risk of something going wrong?
Which defects would be particularly problematic for users or the business?
Professional testing therefore always involves setting priorities based on potential risks.
What Does a Software Tester Actually Do?
The work can vary considerably from one project to another.
One important point first: Testing is not an individual activity – it is teamwork. Developers, Product Owners, and domain experts also test as part of their day-to-day work, for example through unit testing, acceptance testing, or collaborative reviews. Specialized testers, however, bring their own perspective, testing expertise, and the necessary degree of independence to the team.
Testers – and anyone else performing testing activities – may, for example:
- challenge requirements,
- identify risks,
- devise meaningful tests,
- explore software in a targeted way,
- prepare test data,
- use automated tests,
- describe identified problems clearly and reproducibly,
- discuss results with the team.
The aim is not to “prove” that developers have made mistakes.
Good testing works best as a team effort.
Ultimately, everyone is working towards the same goal: developing a product that works as well as possible and fulfils its intended purpose.
Manual Testing or Automation?
This is not an either-or question either.
Automated tests are extremely useful when certain checks need to be repeated regularly. A computer can execute these tests quickly and consistently.
But automation cannot decide for itself what is worth testing.
Someone first has to understand:
What could go wrong?
What matters?
Which cases are particularly interesting?
Where does automation actually make sense?
That is why software testing, even with increasingly powerful tools, remains an activity in which critical thinking, experience, and curiosity play a major role.
Software Testing Means Asking Good Questions
If you take away just one idea from this article, let it be this:
Software testing is not simply about clicking through finished software and looking for defects.
Testers try to understand how a product actually behaves.
They ask questions.
They look for risks.
They try things that others may not have considered.
And they provide information about where a product works well and where problems remain.
This information helps teams make better decisions – and, as a result, build better software.
How Can I Learn More About Software Testing?
If you want to start a career in software testing or give more structure to the knowledge you already have, there are many areas you can explore in greater depth: test techniques, test automation, risk-based testing, or collaboration within a development team.
One way to build a solid foundation is the ISTQB® Certified Tester Foundation Level (CTFL). It provides a structured introduction to the fundamentals of professional software testing.
Would you like to learn software testing from the ground up or equip your team with practical testing skills? Whether you are looking for ISTQB® CTFL certification or tailored training, just get in touch with us. Together, we will find the right format.
FAQ
What Is Software Testing in Simple Terms?
Software testing comprises activities used to investigate and evaluate the quality of software and other work products. Among other things, its objectives are to detect failures and defects, identify quality risks, and provide information for decision-making. Testing therefore involves more than simply executing software.
Why Is Software Testing Important?
Software testing helps identify failures and quality risks before or while software is in use. The information gained helps teams, for example, fix defects, assess risks, and make better-informed release decisions.
What Does a Software Tester Do?
Software testers analyse requirements and risks, plan tests, design test cases, prepare and execute tests, and evaluate and communicate the results. The exact activities vary considerably depending on the project and team.
Does Software Testing Only Take Place Once the Software Is Finished?
No. Testing can begin with requirements, user stories, designs, or other work products. Reviews and static analysis, for example, do not require executable software. Early testing can help identify problems before they propagate into later work products.
Can Testing Make Software Defect-Free?
Testing can show that defects are present, but it cannot prove that no defects remain. For real-world software systems, exhaustive testing is generally impossible. Tests are therefore selected based on objectives, risks, and context.
Is Software Testing the Same as Quality Assurance?
No. In ISTQB® terminology, testing is product-oriented and a form of quality control. Quality assurance is more process-oriented and preventive: it focuses on establishing and improving processes so that good quality is more likely to be achieved.
Do I Need Programming Skills to Become a Software Tester?
Programming skills are not essential for every testing activity. Analytical thinking, communication skills, curiosity, domain knowledge, and a systematic approach to risks are also important. Technical knowledge and programming skills, however, become particularly valuable in more technical roles and in test automation.
What Is the ISTQB® Certified Tester Foundation Level?
The ISTQB® Certified Tester Foundation Level, or CTFL for short, provides fundamental knowledge and a common terminology for professional software testing. Among other topics, it covers the fundamentals of testing, testing throughout the software development lifecycle, static testing, test analysis and design, test management, and test tools.