THE V-MODEL OF SOFTWARE TESTING

Software testing is too  important to leave to the end of the project, and the V-Model of testing incorporates testing into
the entire software development life cycle.  In a diagram of the V-Model, the V proceeds down and then up, from
left to right depicting the basic sequence of development and testing activities. The model highlights the
existence of different levels of testing and depicts the way each relates to a different development phase.
Like any model, the V-Model has detractors and arguably has deficiencies and alternatives but it clearly illustrates that
testing can and should start at the very beginning of the project.  (See Goldsmith for a summary of the pros and cons
and an alternative.  Marrik’s articles provide criticism and an alternative.)  In the requirements gathering stage the
business requirements can verify and validate the business case used to justify the project.  The business
requirements are also used to guide the user acceptance testing.   The model illustrates how each subsequent phase
should verify and validate work done in the previous phase, and how work done during development is used to guide
the individual testing phases.  This interconnectedness lets us identify important errors, omissions, and other
problems before they can do serious harm.  Application testing begins with Unit Testing, and in the section titled

  " Types of Tests ” we will discuss each of these test phases in more detail.