What Is Software Testing? (Types & Examples)

Software is everywhere. It powers the apps on your phone, the systems your bank relies on, the platforms your organisation uses to serve its customers, and the tools your team depends on every day. When software works well, it's invisible. When it doesn't, the consequences range from minor frustration to serious financial or reputational damage.

Software testing is the discipline that sits between development and delivery, providing the confidence that what has been built actually works as intended. But testing is not a single activity. It encompasses a wide range of approaches, techniques, and types, with each suited to different situations, risks, and quality concerns.

If you're new to the field or simply looking to build a clearer picture of what testing involves, this guide explains what software testing is, why it matters, and walks through the main types of software testing, with practical testing examples to bring each one to life.

What is software testing?

Software testing is the process of evaluating software to identify defects, verify that it meets requirements, and build confidence that it is fit for its intended purpose. It involves executing software functions under controlled conditions, observing the behaviour, and then comparing that behaviour against what you expected.

Testing is there to find bugs, but it is also about providing information that helps teams make informed decisions about quality and risk. A well-tested release gives stakeholders (and developers) confidence. A poorly tested one creates uncertainty and potentially costly problems after release.

Good testing starts early. Rather than waiting until development is complete, effective teams integrate testing throughout the software development lifecycle, from reviewing requirements to validating the finished product. The earlier a defect is found, usually the cheaper and easier it is to fix.

Why software testing matters

The cost of defects increases significantly the later they are discovered. A requirement that is misunderstood at the design stage costs very little to correct. The same misunderstanding, found after release, can cost many times more to fix, whether that’s in development effort, customer impact, or reputational damage. For example, CISQ even reports that poor software has cost US firms $2.41 trillion.

Beyond cost, testing matters because users expect software to work. A payment that fails, a form that doesn't submit, or an app that crashes under normal use erodes trust quickly. A business relies on software quality; it isn’t just a minor technical issue, but what a brand represents.

Testing also plays an increasingly important role in compliance and governance. In regulated industries such as finance, healthcare, and government, organisations must be able to demonstrate that their software has been rigorously tested and that quality decisions are documented and traceable.

The main types of software testing

There are so many different types of testing and techniques available to software testers. Understanding the different types of software testing helps teams make deliberate decisions about where to focus their effort and which approaches are most appropriate for a given situation.

Functional testing

Functional testing verifies that the software does what it is supposed to do. It checks that features and user journeys work correctly according to the requirements, without concern for how the underlying code achieves this.

Functional testing example: A tester verifying an online checkout process confirms that a user can add items to a basket, enter payment details, and receive an order confirmation. Each step is checked against the expected outcome defined in the requirements or acceptance criteria.

Non-functional testing

Non-functional testing evaluates how the software performs, rather than what it does. It covers areas such as speed, reliability, security, usability, and accessibility, qualities that are often just as important to users as functional correctness.

Non-functional testing example: A performance test checks how an e-commerce website responds when 10,000 users access it simultaneously during a sale event, identifying the point at which response times degrade and where bottlenecks occur.

Unit testing

Unit testing focuses on individual components or functions of the code in isolation. It is typically carried out by developers as part of the development process to verify that each unit of code behaves correctly on its own before it is integrated with other parts of the system.

Unit testing example: A developer writes a unit test to verify that a function calculating VAT on a purchase returns the correct value for a range of input amounts, including edge cases such as zero and negative values.

Integration testing

Integration testing checks how different components or systems work together. Even when individual units function correctly in isolation, combining them can introduce new defects at the boundaries between components.

Integration testing example: After separately testing a payment service and an order management system, an integration test verifies that a completed payment correctly triggers an order confirmation and updates stock levels in the connected inventory system.

System testing

System testing evaluates the complete, integrated software product against its requirements. It tests the system as a whole, from end to end, in an environment that closely resembles production.

System testing example: A tester working on a mobile banking app runs a full system test that covers account login, balance enquiry, fund transfer, statement download, and logout, verifying that the entire application functions correctly as an integrated product.

Regression testing

Regression testing verifies that existing functionality continues to work correctly after changes are made to the software. Every time new features are added or defects are fixed, there is a risk that something previously working has been unintentionally broken.

Regression testing example: Following an update to a travel booking platform's search algorithm, regression tests are run across all existing booking journeys to confirm that flight search, seat selection, payment, and confirmation all continue to work as expected.

Acceptance testing

Acceptance testing determines whether the software meets the needs of its users and stakeholders and is ready for release. It is often the final stage of testing before a product goes live, and may involve end users or business representatives rather than dedicated testers.

Acceptance testing example: Before launching a new HR self-service portal, a group of employees from across the organisation test common tasks such as booking annual leave, submitting expenses, and updating personal details, confirming the system works as expected in real-world use.

Exploratory testing

Exploratory testing is a simultaneous process of learning, test design, and execution. Rather than following a predefined script, the tester uses their knowledge, curiosity, and judgement to investigate the software dynamically, often uncovering defects that scripted tests would miss.

Exploratory testing example: A tester exploring a newly released messaging feature tries a series of unexpected inputs such as very long messages, special characters, rapid successive sends, and switching between network types mid-send, to discover how the feature behaves under conditions that weren't explicitly anticipated.

Usability testing

Usability testing evaluates how easy and intuitive the software is to use. It focuses on the user experience, identifying areas where users struggle, make errors, or find the interface confusing.

Usability testing example: A group of first-time users are observed attempting to complete a series of tasks on a new insurance comparison website. Their behaviour, hesitations, and errors are recorded to identify where the interface can be improved before launch.

Security testing

Security testing identifies vulnerabilities that could be exploited to compromise the software, its data, or its users. It covers areas such as authentication, authorisation, data encryption, and protection against common attack types.

Security testing example: A security tester attempts to access restricted areas of a web application without valid credentials, tests for SQL injection vulnerabilities in input fields, and verifies that sensitive data is encrypted both in transit and at rest.

Compatibility testing

Compatibility testing verifies that the software works correctly across different environments, including operating systems, browsers, devices, and screen sizes. It is particularly important for web and mobile applications, where users access software from a wide variety of configurations.

Compatibility testing example: A web application is tested across Chrome, Firefox, Safari, and Edge on both Windows and macOS, as well as on iOS and Android devices, to confirm consistent behaviour and appearance across all supported environments.

Choosing the right types of software testing

No single type of testing covers everything. Effective test strategies combine multiple types of software testing, selected based on the nature of the product, the risks involved, and the stage of development.

A risk-based approach helps teams prioritise their testing effort, focusing most heavily on areas where defects would have the greatest impact, while applying lighter coverage to lower-risk areas. This is especially important in agile and DevOps environments, where time is constrained, and releases are frequent.

Automation plays a key role in making testing sustainable at pace. Regression tests, unit tests, and integration tests are well-suited to automation, allowing teams to run large volumes of checks quickly and consistently with every build. Exploratory, usability, and acceptance testing, by contrast, rely on human judgement and are typically kept manual.

Building a career in software testing

Understanding the types of software testing and how to apply them effectively is the foundation of a strong testing career. But knowledge alone is not enough, testers also need the practical skills to design good tests, think critically about risk, and communicate quality clearly to their teams and stakeholders.

Structured training and recognised certification provide the frameworks that help testers develop these capabilities systematically, building confidence and credibility alongside practical ability.

How TSG Training can help

At TSG Training, our courses are built around the knowledge and skills that make testers genuinely effective, from foundational principles and types of software testing through to specialist areas such as automation, agile, and test management.

Whether you are new to the profession or looking to deepen your expertise, explore our software testing courses and ISTQB certification courses to find the right programme for where you are in your career.