Software testing is the process of evaluating a software application to find defects and to confirm that it behaves as expected. At its heart it answers two questions: does the software do what it should, and does it avoid doing what it should not? Testing gives stakeholders information about the quality of the product and the risk of releasing it.
Every piece of software is built by people, and people make mistakes. A mistake in the code is a defect (or bug); when that defect is executed it can cause a failure — the software behaving incorrectly. Testing is how we find those defects before our users do.
The testing process in simple terms
The basic flow of testing
Why it is more than "just clicking around"
Good testing is a disciplined, thoughtful activity. It involves understanding the requirements, designing test cases that give meaningful coverage, preparing realistic data, executing tests methodically, and reporting results clearly. It is as much about managing risk as it is about finding bugs — no team can test everything, so testers focus effort where failure would hurt most.
Verification and validation
Two ideas sit at the core of testing. Verification asks "are we building the product right?" — checking it against its specification. Validation asks "are we building the right product?" — checking it meets the user's real needs. Both matter, and we explore them in detail later in this series.
Conclusion
Software testing is the systematic search for defects and the evidence that software is fit for use. It protects users, reputations, and budgets by catching problems early. The rest of this section builds on this foundation, from why testing matters to the techniques and processes that make it effective.