External vs Inhouse Testing

Independent testing and IV&V  vs  software developers' testing

• Testing is a particular engineering discipline. It requires special methodologies, tools, knowledge, skills, experience, and peculiar talent.
   
• The aim of programmers is to prove that the program works. Put simple, testers' task is to detect faults (i.e., prove that the program doesn't work) and make sure that the program meets user's requirements and is convenient in usage. These two views at the program are quite different.
   
• Programmers get used to the code, and can unconsciously avoid some bottlenecks in the program when they test it. It is an objective process. "Programmers can't test their own work. It is the same as proof reading a letter you write, you just don't see the mistakes that others find" ("Golden rules" of software testing).
  
  That is why all software development methodologies require Review activities. In its essence the external independent testing is one of them.
   
• At software companies junior programmers are rather often engaged as testers. Of course, they consider testing only as the first step to programming. As a result, they don't have a stimulus to be properly trained in testing or to improve their testing view and intuition.
   
• But it is much worse when
     - improper management,
     - insufficient commitment to the project,
     - lack of proficiency or resources,
     - high personnel attrition,
     - tight deadline or limited budget (i.e. results of bad planning or "to win the tender at any cost"), etc.
  can compel a development team to neglect the quality. An in-house testing team can be under financial and administrative dependence on a project manager and unable to resist that.
  
  Independent quality control and IV&V is the only way to reveal and prevent such dangerous actions and the impendent project failure.