Home Topics What is Software Testing and How Does it Work? What is software testing?
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What is software testing?

Software testing is the process of evaluating and verifying that a software product or application does what it’s supposed to do. The benefits of good testing include preventing bugs and improving performance.

Verify and validate application quality to ensure it meets user requirements

Software testing today is most effective when it is continuous, indicating that testing is started during the design, continues as the software is built out, and even occurs when deployed into production. Continuous testing means that organizations don’t have to wait for all the pieces to be deployed before testing can start. Shift-left, which is moving testing closer to design, and shift-right, where end-users perform validation, are also philosophies of testing that have recently gained traction in the software community. When your test strategy and management plans are understood, automation of all aspects of testing becomes essential to support the speed of delivery that is required.

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Types of software testing

There are many different types of software tests, each with specific objectives and strategies:

  • Acceptance testing: Verifying whether the whole system works as intended.
  • Code review: Confirming that new and modified software is following an organization’s coding standards and adheres to its best practices.
  • Integration testing: Ensuring that software components or functions operate together.
  • Unit testing: Validating that each software unit runs as expected. A unit is the smallest testable component of an application.
  • Functional testing: Checking functions by emulating business scenarios, based on functional requirements. Black-box testing is a common way to verify functions.
  • Performance testing: Testing how the software runs under different workloads. Load testing, for example, is used to evaluate performance under real-life load conditions.
  • Regression testing: Checking whether new features break or degrade functionality. Sanity testing can be used to verify menus, functions and commands at the surface level, when there is no time for a full regression test.
  • Security testing: Validating that your software is not open to hackers or other malicious types of vulnerabilities that might be exploited to deny access to your services or cause them to perform incorrectly.
  • Stress testing: Testing how much strain the system can take before it fails. Stress testing is considered to be a type of non-functional testing.
  • Usability testing: Validating how well a customer can use a system or web application to complete a task.

In each case, validating base requirements is a critical assessment. Just as important, exploratory testing helps a tester or testing team uncover hard-to-predict scenarios and situations that can lead to software errors.

Even a simple application can be subject to a large number and variety of tests. A test management plan helps to prioritize which types of testing provide the most value—given available time and resources. Testing effectiveness is optimized by running the fewest number of tests to find the largest number of defects.

Test management plan
History of software testing

Software testing arrived alongside the development of software, which had its beginnings just after World War II. Computer scientist Tom Kilburn is credited with writing the first piece of software, which debuted on 21 June 1948 at the University of Manchester in England. It performed mathematical calculations by using machine code instructions.

Debugging was the main testing method at the time and remained so for the next two decades. By the 1980s, development teams looked beyond isolating and fixing software bugs to testing applications in real-world settings. It set the stage for a broader view of testing, which encompassed a quality assurance process that was part of the software development lifecycle.

Software development
Why software testing is important

Few can argue against the need for quality control when developing software. Late delivery or software defects can damage a brand’s reputation, which leads to frustrated and lost customers. In extreme cases, a bug or defect can degrade interconnected systems or cause serious malfunctions.

Consider Nissan having to recall over 1 million cars due to a software defect in the airbag sensor detectors, or a software bug that caused the failure of a USD 1.2 billion military satellite launch.1 The numbers speak for themselves. Software failures in the US cost the economy USD 1.1 trillion in assets in 2016. What’s more, they impacted 4.4 billion customers.2

Though testing itself costs money, companies can save millions per year in development and support if they have a good testing technique and QA processes in place. Early software testing uncovers problems before a product goes to market. The sooner development teams receive test feedback, the sooner they can address issues such as:

  • Architectural flaws
  • Poor design decisions
  • Invalid or incorrect functionality
  • Security vulnerabilities
  • Scalability issues

When development leaves ample room for testing, it improves software reliability and high-quality applications are delivered with few errors. A system that meets or even exceeds customer expectations leads to potentially more sales and greater market share.

Software testing best practices

Software testing follows a common process. Tasks or steps include defining the test environment, developing test cases, writing scripts, analyzing test results and submitting defect reports.

Testing can be time-consuming. Manual testing or ad hoc testing might be enough for small builds. However, for larger systems, tools are frequently used to automate tasks. Automated testing helps teams implement different scenarios, test differentiators (such as moving components into a cloud environment), and quickly get feedback on what works and what doesn't.

A good testing approach encompasses the application programming interface (API), user interface and system levels. The more tests that are automated, and run early, the better. Some teams build in-house test automation tools. However, vendor solutions offer features that can streamline key test management tasks such as:

Continuous testing

Project teams test each build as it becomes available. This type of software testing relies on test automation that is integrated with the deployment process. It enables software to be validated in realistic test environments earlier in the process, which improves design and reduces risks.

Configuration management

Organizations centrally maintain test assets and track what software builds to test. Teams gain access to assets such as code, requirements, design documents, models, test scripts and test results. Good systems include user authentication and audit trails to help teams meet compliance requirements with minimal administrative effort.

Service virtualization

Testing environments might not be available, especially early in code development. Service virtualization simulates the services and systems that are missing or not yet completed, enabling teams to reduce dependencies and test sooner. They can reuse, deploy and change a configuration to test different scenarios without having to modify the original environment.

Defect or bug tracking

Monitoring defects is important to both testing and development teams for measuring and improving quality. Automated tools allow teams to track defects, measure their scope and impact, and uncover related issues.

Metrics and reporting

Reporting and analytics enable team members to share status, goals and test results. Advanced tools integrate project metrics and present results in a dashboard. Teams quickly see the overall health of a project and can monitor relationships between test, development and other project elements.

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1 "What is Software Testing?" (link resides outside ibm.com), Thomas Hamilton, guru99.com, updated 3 January 2024

2 "The glitch economy: Counting the cost of software failures" (link resides outside ibm.com), Dalibor Siroky, 30 October 2017