Why do we need to Test?
Defects can exist in the software, as
it is developed by human who can make mistakes during the development
of software. However, it is the primary duty of a software vendor to
ensure that software delivered does not have defects and the customers
day-to-day operations do not get affected. This can be achieved by
rigorously testing the software. The most common origin of software
bugs is due to:
• Poor understanding and incomplete requirements
• Unrealistic schedule
• Fast changes in requirements
• Too many assumptions and complacency
Some
of major computer system failures listed below gives ample evidence
that the testing is an important activity of the software quality
process.
1. In April of 1999 a software bug caused
the failure of a $1.2 billion military satellite launch, the costliest
unmanned accident in the history of Cape Canaveral launches. The
failure was the latest in a string of launch failures, triggering a
complete military and industry review of U.S. space launch programs,
including software integration and testing processes. Congressional
oversight hearings were requested.
2. On June 4 1996 the first
flight of the European Space Agency's new Ariane 5 rocket failed
shortly after launching, resulting in an estimated uninsured loss of a
half billion dollars. It was reportedly due to the lack of exception
handling of a floating-point error in a conversion from a 64-bit
integer to a 16-bit signed integer.
3. The computer system of
a major online U.S. stock trading service failed during trading hours
several times over a period of days in February of 1999 according to
nationwide news reports. The problem was reportedly due to bugs in a
software upgrade intended to speed online trade confirmations.
4. In
November of 1997 the stock of a major health industry company dropped
60% due to reports of failures in computer billing systems, problems
with a large database conversion, and inadequate software testing. It
was reported that more than $100,000,000 in receivables had to be
written off and that multi-million dollar fines were levied on the
company by government agencies.
5. Software bugs caused the
bank accounts of 823 customers of a major U.S. bank to be credited with
$924,844,208.32 each in May of 1996, according to newspaper reports.
The American Bankers Association claimed it was the largest such error
in banking history. A bank spokesman said the programming errors were
corrected and all funds were recovered.
All the above incidents
only reiterate the significance of thorough testing of software
applications and products before they are put on production. It clearly
demonstrates that cost of rectifying defect during development is much
less than rectifying a defect in production.
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