software life cycle

Testing throughout the software life cycle
Important Terms:
Software development models
COTS, interactive-incremental development model, validation, verification, V-model.
Test levels
Alfa testing, beta testing, component testing (also known as unit/module/program testing), driver, stub, field testing, functional requirement, non-functional requirement, integration, integration testing, robustness testing, system testing, test level, test-driven development, test environment, user acceptance testing.
Test types
Black box testing, code coverage, functional testing, interoperability testing, load testing, maintainability testing, performance testing, portability testing, reliability testing, security testing, specification based testing, stress testing, structural testing, usability testing, white box testing 
Maintenance testing
Impact analysis, maintenance testing.
i) Software development models
a) V-model (sequential development model)
Although variants of the V-model exist, a common type of V-model uses four test levels,
corresponding to the four development levels.
The four levels used in this syllabus are:
  • component (unit) testing;
  • integration testing;
  • system testing;
  • acceptance testing.
b) Iterative-incremental development models
Iterative-incremental development is the process of establishing requirements, designing, building and testing a system, done as a series of shorter development cycles. Examples are: prototyping, rapid application development (RAD), Rational Unified Process (RUP) and agile development models.
c) Testing within a life cycle model
In any life cycle model, there are several characteristics of good testing:
  • For every development activity there is a corresponding testing activity.
  • Each test level has test objectives specific to that level.
  • The analysis and design of tests for a given test level should begin during the corresponding development activity.
  • Testers should be involved in reviewing documents as soon as drafts are available in the development life cycle.
ii) Test levels
a) Component testing
Component testing searches for defects in, and verifies the functioning of, software (e.g. modules, programs, objects, classes, etc.) that are separately testable.
Component testing may include testing of functionality and specific non-functional characteristics, such as resource-behaviour (e.g. memory leaks) or robustness testing, as well as structural testing (e.g. branch coverage).
One approach to component testing is to prepare and automate test cases before coding. This is called a test-first approach or test-driven development.
b) Integration testing
Integration testing tests interfaces between components, interactions with different parts of a system, such as the operating system, file system, hardware, or interfaces between systems.
Component integration testing tests the interactions between software components and is done after component testing;
System integration testing tests the interactions between different systems and may be done after system testing.
Testing of specific non-functional characteristics (e.g. performance) may be included in integration testing.
c) System testing
System testing is concerned with the behaviour of a whole system/product as defined by the scope of a development project or programme.
In system testing, the test environment should correspond to the final target or production environment as much as possible in order to minimize the risk of environment-specific failures not being found in testing.
System testing may include tests based on risks and/or on requirements specifications, business processes, use cases, or other high level descriptions of system behaviour, interactions with the operating system, and system resources.
System testing should investigate both functional and non-functional requirements of the system.
d) Acceptance testing
Acceptance testing is often the responsibility of the customers or users of a system; other stakeholders may be involved as well.
The goal in acceptance testing is to establish confidence in the system, parts of the system or specific non-functional characteristics of the system
Contract and regulation acceptance testing
Contract acceptance testing is performed against a contract’s acceptance criteria for producing custom-developed software. Acceptance criteria should be defined when the contract is agreed. Regulation acceptance testing is performed against any regulations that must be adhered to, such as governmental, legal or safety regulations.
Alpha and beta (or field) testing
Alpha testing is performed at the developing organization’s site. Beta testing, or field testing, is performed by people at their own locations. Both are performed by potential customers, not the developers of the product.
iii) Test types
a) Testing of function (functional testing)
The functions that a system, subsystem or component are to perform may be described in work products such as a requirements specification, use cases, or a functional specification, or they may be undocumented. The functions are “what” the system does.
A type of functional testing, security testing, investigates the functions (e.g. a firewall) relating to detection of threats, such as viruses, from malicious outsiders. Another type of functional testing, interoperability testing, evaluates the capability of the software product to interact with one or more specified components or systems.
b) Testing of non-functional software characteristics (non-functional testing)
Non-functional testing includes, but is not limited to, performance testing, load testing, stress testing, usability testing, maintainability testing, reliability testing and portability testing. It is the testing of “how” the system works.
Non-functional testing may be performed at all test levels.
c) Testing of software structure/architecture (structural testing)
Structural (white-box) testing may be performed at all test levels. Structural techniques are best used after specification-based techniques, in order to help measure the thoroughness of testing through assessment of coverage of a type of structure.
Structural testing approaches can also be applied at system, system integration or acceptance testing levels (e.g. to business models or menu structures).
d) Testing related to changes (confirmation testing (retesting) and regression testing)
After a defect is detected and fixed, the software should be retested to confirm that the original defect has been successfully removed. This is called confirmation. Debugging (defect fixing) is a development activity, not a testing activity.
Regression testing is the repeated testing of an already tested program, after modification, to discover any defects introduced or uncovered as a result of the change(s). It is
performed when the software, or its environment, is changed.
Regression testing may be performed at all test levels, and applies to functional, non-functional and structural testing.
iv) Maintenance testing
Once deployed, a software system is often in service for years or decades. During this time the system and its environment are often corrected, changed or extended.
Modifications include planned enhancement changes (e.g. release-based), corrective and
emergency changes, and changes of environment,
Maintenance testing for migration (e.g. from one platform to another) should include operational tests of the new environment, as well as of the changed software.
Maintenance testing for the retirement of a system may include the testing of data migration or archiving if long data-retention periods are required.
Maintenance testing may be done at any or all test levels and for any or all test types.



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