Why Do We Test a Software?

What is the need to test a software? Why should a company have a team for software testing and quality assurance? Why to test ? These are some questions, every Software Tester has to face regularly throughout his testing career. Let me try and give an one sentence answer to all these question.

To Reduce Costly Errors
The cost of errors in software can vary from nothing at all to large amounts of money and even the loss of life. There are hundreds of stories about failures of computer systems that have been attributed to errors in software. There are many reasons why systems fail but the issue that stands out the most is the lack of adequate testing.

These well documented stories emphasise the necessity for correct and thorough testing, as the risks involved were not just measured in financial terms but in human lives! There are complete disasters that have occurred in the development of new systems that have caused huge financial losses, which could have been avoided through effective testing.

Examples

Pepsi - $42 Billion Error

In May 1992, Pepsi ran a promotion in the Philippines. It told customers they could win a million pesos (approx. $40,000) if they bought a bottle of Pepsi and found number 349 stamped on the underside of the bottle cap. Unfortunately, due to a software error, 800,000 bottle caps were produced with number 349 instead of one, which was an equivalent of $42 billion in prize money. It cost the company dearly as some people pursued their claims through the courts and Pepsi paid out millions of dollars in compensation.

Cahoot - Web Site Failure
Cahoot, Abbey National's online bank, was launched June 2000. On its first day of operation, within 90 minutes of trading, the system failed, causing the website to crash.

This was caused by high customer demand placed on the site following Cahoot's successful marketing incentive scheme. It was later discovered that the registration application and its integration with the network were not fully tested.

The system should have been designed to cope with this surge of website hits and high volume of concurrent users. If a web-based load and performance test had been carried out earlier within the development life cycle of the project, this applications server bottleneck could have been identified prior to going live.

Chemical Bank
Another story was printed in the New York Times in February 1994. Chemical Bank managed to allow $15 million to be withdrawn incorrectly from 100,000 accounts - a single line error in the program caused every ATM on their network to process the transaction twice.

And the bottomline is each of these errors could have been avoided with effective testing of the software. So we test to avoid/reduce costly errors.

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About Debasis Pradhan

Debasis has over a decade worth of exclusive experience in the field of Software Quality Assurance, Software Development and Testing. He writes here to share some of his interesting experiences with fellow testers.