Testing Life Cycle part one

Often, testing after coding is the only method used to determine the adequacy of the system. When testing is constrained to a single phase and confined to the later stages of development, severe consequences can develop.

It is not unusual to hear of testing consuming 50 percent of the development budget. All errors are costly, but the later in the life cycle that the error discovered is made, the more costly the error.

An error discovered in the latter parts of the life cycle must be paid for four different times.

The first cost is developing the program erroneously, which may include writing the wrong specifications, coding the system wrong, and documenting the system improperly.

Second, the system must be tested to detect the error.

Third, the wrong specifications and coding must be removed and the proper specifications, coding, and documentation added.

Fourth, the system must be retested to determine that it is now correct.

If lower cost and higher quality systems are the information services goals, verification must not be isolated to a single phase in the development process, but rather, incorporated into each phase of development.

One of the most prevalent and costly mistakes on systems development projects today is to defer the activity of detecting and correcting problems until late in the project. A major justification for an early verification activity is that many costly errors are made before coding begins.

Studies have shown that the majority of system errors occur in the design phase. These numerous studies show that approximately two-thirds of all detected system errors can be attributed to errors made during the design phase. This means that almost two-thirds of the errors must be specified and coded into programs before they can be detected.

The recommended testing process is presented in Table 1-5 as a life cycle chart showing the verification activities for each phase. The success of conducting verification throughout the development cycle depends upon the existence of clearly defined and stated products at each development stage.

The more formal and precise the statement of the development product, the more amenable it is to the analysis required to support verification. Many of the new system development methodologies encourage firm products even in the early development stages.

The recommended test process involves testing in every phase of the life cycle. During the requirements phase, the emphasis is upon validation to determine that the defined requirements meet the needs of the organization. During the design and program phases, the emphasis is on verification to ensure that the design and programs accomplish the defined requirements.

During the test and installation phases, the emphasis is on inspection to determine that the implemented system meets the system specification. During the maintenance phases, the system will be retested to determine that the changes work and that the unchanged portion continues to work.



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