Software systems are an increasing part of life, from business applications (e.g. banking) to consumer products (e.g. cars). Most people have had an experience with software that did not work as expected. Software that does not work correctly can lead to many problems, including loss of money, time or business reputation, and could even cause injury or death.
A human being can make an error (mistake), which produces a defect (fault, bug) in the code, in software or a system, or in a document. If a defect in code is executed, the system will fail to do what it should do (or do something it shouldn’t), causing a failure. Defects in software, systems or documents may result in failures, but not all defects do so.
Defects occur because human beings are fallible and because there is time pressure, complex code, complexity of infrastructure, changed technologies, and/or many system interactions. Failures can be caused by environmental conditions as well: radiation, magnetism, electronic fields, and pollution can cause faults in firmware or influence the execution of software by changing hardware conditions.
Rigorous testing of systems and documentation can help to reduce the risk of problems occurring during operation and contribute to the quality of the software system, if defects found are corrected before the system is released for operational use. Software testing may also be required to meet contractual or legal requirements, or industry-specific standards.
With the help of testing, it is possible to measure the quality of software in terms of defects found, for both functional and non-functional software requirements and characteristics (e.g. reliability, usability, efficiency, maintainability and portability).
Testing can give confidence in the quality of the software if it finds few or no defects. A properly designed test that passes reduces the overall level of risk in a system. When testing does find defects, the quality of the software system increases when those defects are fixed. Lessons should be learned from previous projects. By understanding the root causes of defects found in other projects, processes can be improved, which in turn should prevent those defects from reoccurring and, as a consequence, improve the quality of future systems. This is an aspect of quality assurance.
Testing should be integrated as one of the quality assurance activities (i.e. alongside development standards, training and defect analysis).
How much testing is enough?
Deciding how much testing is enough should take account of the level of risk, including technicaland business product and project risks, and project constraints such as time and budget. Testing should provide sufficient information to stakeholders to make informed decisions about the release of the software or system being tested, for the next development step or handover to customers.
Testing all day long