Test - t timecriticalsystems undependable t t Khansari...

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Khansari – Advanced Programming Software testing Issues in Software Testing Increasing demand for high software quality  time-critical systems  safety-critical systems Software systems have a reputation for being  undependable.   Build confidence that the system will work  without error after testing is the goal 
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Khansari – Advanced Programming Software testing Explosion of Ariane 5 Loss destroyed 40 seconds after liftoff,  $500 million loss (June 4, 1996) Software Bug  mapping 64-bit float to 16-bit signed caused “horizontal velocity” to  exceed 32767. software exception activated  automatic destruct
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Khansari – Advanced Programming Software testing Failure of Therac 25 Radiation Treatment Machine made by  Atomic Energy of Canada, Ltd. Loss (1985-1987) Four patients killed Huge lawsuit Software Bug Delivered maximum power regardless of  operator’s setting
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Khansari – Advanced Programming Software testing Patriot Missile Failure on February 25, 1991 Patriot Failed to track Scud Missile 28 soldiers killed, 100 injured Software Bug  1/10th (in binary) =  0.000110011001100110011001100110011001100 …… Truncation to 24 bits causes error of about  0.000000095 decimal. In 100 hours, this added up to 500 meters
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Khansari – Advanced Programming Software testing What Makes Testing So Difficult? Inherent complexity of software Constructing an operational environment for  testing purpose Intractable and undecidable nature of testing Errors manifest themselves in rare states, yet  crucially important.    Murphy’s Law
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Khansari – Advanced Programming Software testing Some More Definitions Error : a mistake made in the process of constructing software (before the software is released to the end user) Fault/bug/defect : the manifestation of an error in the software (After the software has been released to the end user) Failure: a condition arising when executing software produces an incorrect result
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Khansari – Advanced Programming Software testing Testing Related Activities Testing Verification &    Validation      (V & V) Quality Assurance
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Khansari – Advanced Programming Software testing Some Definitions Verification : has the program been implemented correctly?
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Test - t timecriticalsystems undependable t t Khansari...

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