Overview of Testing - Software Testing: Testing Across the Entire Software Development Life Cycle - page 21

realized during the current testing projects by the intelligent use of automated testing
tools. In the right situations, automated testing tools can reduce the overall cost of
testing when compared with the same testing done manually. Other benefi ts can be
realized on the next testing projects by the reuse of testing scripts and the reuse of
defect discovery patterns. When testing scripts are written, validated, and executed,
they constitute reusable intelligence for the system being scripted. This “canned”
knowledge can be applied to the next version of the same system or to new systems
with similar functionality. The technique of reusing test scripts on a subsequent version
is called regression testing . Defect discovery patterns, when collected over a number
of development projects, can be used to more accurately forecast the completion of
testing. These same testing histories can also be used to verify that improvements
in development processes really do improve the system being developed. Historical
defect patterns and their usefulness are explored in Chapter 12.

1.4.3 The Game of “Gossip”

Capers Jones, has some revealing information about the source of software defects.
Figure 1.3 shows a plot of his fi ndings on the same software development axis as the
defect correction cost plot. [10B]

Figure 1.3 Percentage of defects. Applied Software Measurement, Capers Jones, 1996

The fi ndings tell us that 85% of all software defects are introduced at the earli-
est phase of development before any code has been executed ! If there is no code
execution, then what is the source of this mountain of defects? The answer is the
documentation, that is, the requirements, the specifi cations, the data design, the pro-
cess design, the interface design, the database structure design, the platform design,