om fasani White Box Testing(con't 2)Could test every path and program may still have errors Does not guarantee program matches specification, L.e. Wrong program Missing paths: would not detect absence of necessary pati Could still have data-sensitivity errors e.g. program has to compare two numbers for convergence if (A-B)< epsilon is wrong because should compare to abs (a-B) Detection of this error dependent on values used for A and B and would not necessarily be found by executing every path through program Computers and Risk Mathematical Modeling Difficulties Large number of states and lack of regularity Lack of physical continuity: requires discrete rather than continuous math Specifications and proofs using logic May be same size or larger than code More difficult to construct than code Harder to understand than code Therefore, as difficult and error-prone as code itself Have not found good ways to measure software qualityc ￾✂✁✂✄☎✁✂✆☎✝✂✞✠✟✌☞✱✩ ✙✝✂✖✠✚✂✛✂✜✁✂✒✆✣✢✂✞✂✤✠✥✧✦✆☎★ White Box Testing (con’t) 2) Could test every path and program may still have errors! Does not guarantee program matches specification, i.e., wrong program. Missing paths: would not detect absence of necessary paths Could still have data−sensitivity errors. e.g. program has to compare two numbers for convergence if (A − B) < epsilon ... is wrong because should compare to abs(A − B) Detection of this error dependent on values used for A and B and would not necessarily be found by executing every path through program. c ￾✂✁✂✄☎✁✂✆☎✝✂✞✠✟✌☞✱✪ ✙✝✂✖✠✚✂✛✂✜✁✂✒✆✣✢✂✞✂✤✠✥✧✦✆☎★ Mathematical Modeling Difficulties Large number of states and lack of regularity Lack of physical continuity: requires discrete rather than continuous math Specifications and proofs using logic: May be same size or larger than code More difficult to construct than code Harder to understand than code Therefore, as difficult and error−prone as code itself Have not found good ways to measure software quality