Errors, defects, and failures are three terms commonly used in the context of software testing and quality assurance.
Error
An error is a human action or decision that produces an incorrect or unexpected result. Errors can occur at any stage of the software development process, from requirements gathering to design, development, and testing. Examples of errors include incorrect calculations, typos, and incorrect assumptions.
Defect
A defect, also known as a bug or an issue, is a flaw in the software that causes it to behave incorrectly or produce incorrect results. Defects can occur because of errors made during software development, as well as due to unforeseen circumstances or external factors. Examples of defects include crashes, incorrect outputs, and incorrect behaviour.
Failure
A failure is the inability of the software to perform a required function. Failures occur when defects are triggered and cause the software to behave incorrectly or crash. Failures can occur in various stages of the software development lifecycle, from development to deployment and maintenance.
Software testing aims to identify and prevent errors and defects before they can cause failures. Testing helps to identify defects and errors early in the development process, allowing them to be corrected before the software is released. It also helps ensure that the software meets the requirements and functions as intended, reducing the risk of failures.