Datasheet

What Is the Big Deal About Testing? ■ 13
This phased approach is a common practice in engineering and
is done to assure the quality of a single unit, before it is verified
as an integrated unit to other units. The positive effects are
obvious:
 When you discover an error before getting too far down
the production line, it pays off in tremendous cost sav-
ings.
 It’s easy to troubleshoot a product or process, or do root-
cause analysis, when each element has been tested. (For
instance, if you’re building a brick wall, each brick has
been tested before being placed in the wall so you know
the problem is in the wall structure — you don’t have to
test the bricks again.)
 You enter every integration step with a known quality of
the components (the bricks).
 Testing is easier because the functionality to be tested is
limited to the component to be tested.
The test phases build on each other and are defined in such a
way that testing can be done as early as possible in the SDLC.
Because cost efficiency is crucial, it typically does not make
sense to enter a test phase before the previous phase has met its
exit criteria. For example, it may not be effective to do Perfor-
mance testing before Unit testing is complete.
The prerequisite for each test phase is that the preceding test
phase was executed successfully to a certain extent. The entry
and exit criteria used for each test phase are called quality
gates. They are introduced at the beginning and end of each
phase and determine the success of the test phases.
Quality goals are requirements that describe the quality char-
acteristics of a software product. Because different people may
be involved, and the timing and the nature of the tests to be
conducted are different, we divide up the test phases, as you
can see in Figure 4.
MQM.book Page 13 Wednesday, May 7, 2008 11:29 AM