WHY DO SOFTWARE TESTING?

A “bug” is really a problem in the code; software testing is focused on finding defects in the final product. Here are some important defects that better testing would have found.

• In February 2003 the U.S. Treasury Department mailed 50,000 Social Security checks without a beneficiary name. A spokesperson said that the missing names were due to a software program maintenance error.
• In July 2001 a “serious flaw” was found in off-the-shelf software that had long been used in systems for tracking U.S. nuclear materials. The software had recently been donated to another country and scientists in that country discovered the problem and told U.S. officials about it.
• In October 1999 the $125 million NASA Mars Climate Orbiter—an interplanetary weather satellite—was lost in space due to a data conversion error. Investigators discovered that software on the spacecraft performed certain calculations in English units (yards) when it should have used metric units (meters).
• In June 1996 the first flight of the European Space Agency's Ariane 5 rocket failed shortly after launching, resulting in an uninsured loss of $500,000,000. The disaster was traced to the lack of exception handling for a floating-point error when a 64-bit integer was converted to a 16-bit signed integer.