The use of these three terms is very common among technology professionals, who use them to describe an unexpected result during program execution or to refer to the cause of that result.
It’s important to have a clear understanding of the basic concepts of these three terms—error, bug, and failure—to grasp the difference between them, and to use them appropriately. It’s easy to confuse these terms in the area of software testing because they are closely related.
In the area of software quality assurance: an error is a human action that produces an incorrect result; a defect, also called a bug, is the manifestation of that error in the code; and a failure is the revelation of the defect when using the system.
We must keep in mind that there is a similarity between a defect and a failure, but the difference between the two lies precisely in the fact that a failure is the visual representation of a defect. That is, when a failure is found during a test run, that component will have a defect.
Relationship between Error, Defect, and Failure
These three concepts go hand in hand: an error can generate one or more defects, and a defect will cause a failure. Software errors will always exist, and therefore, the other related concepts will also exist.
Remember that defects are not the only source of software failures; for example, unexpected changes to libraries or systems that many companies depend on can also result in failures.
