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Protocol Analysis/Testing

Protocol Analysis/Testing. Based on Sidhu et al in IEEE TSE 89 and TN 93 Figures from the papers. Basic Idea. Given a protocol spec, how do you know if an implementation conforms to it (conformance testing) Use black-box testing methods Give input, see if output is “right” per spec

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Protocol Analysis/Testing

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  1. Protocol Analysis/Testing Based on Sidhu et al in IEEE TSE 89 and TN 93 Figures from the papers.

  2. Basic Idea • Given a protocol spec, how do you know if an implementation conforms to it (conformance testing) • Use black-box testing methods • Give input, see if output is “right” per spec • Need a formal specification • What input / output pairs should be checked • Fault coverage • Automatic generation

  3. Mealy Machine • Is an FSM that produces an output on each transition. • Minimal – least number of states • Completely Specified – each state has a transition for every input symbol • Strongly connected – if there is a transition path for each state pair • Test subsequence, subsequence, test sequence, optimized test sequence

  4. An Example Mealy Machine

  5. Protocol Modelling • Model protocol as Mealy Machine • Protocol specified state/input combinations are core, others are noncore • Strong vs Weak Conformance • Weak if similar behavior on core, unspeficied on noncore • Analyze coverage via simulation using mutated machines • Showing that machines are equivalent ?

  6. Basic Test generation methods • T-Method • Assume minimal, strongly connected, completely specified machine • Generate random inputs till machine has traversed each transition once, eliminate loops • U-Method • Assume minimal, strongly connected, completely specified machine • Derive Unique IO sequence for each state • For each transition (si,sj), reset, find shortest path from 0 to si, add input to cause transition to sj, add UIO • Beta sequence is concatenation of each subsequence, create optimized sequence.

  7. More test generation methods • D-Method • Assume minimal, strongly connected, completely specified machine with distinguishing sequence • Construct the same way as U method but replace UIO with DS • W-Method • Assume minimal, strongly connected, completely specified machine • Derive a Characterizing set W • Set of input strings a s.t the last output symbol obtained by applying these strings in a fixed order is different for different states. • Use these instead of UIOs

  8. Testing issues • Finding shortest test sequence to check a given set of behaviors • How long to give complete coverage ? • Can we create a hierarchy of sequences • State cardinality may differ in spec and implementation – masking behavior is different • Test subsequence to test (p,q) transition can be viewed as L1.L2…Lk.CS(q) • Bk test subsequence has an L sequence of length k. B0 tests a state. Every Bk is proper subsequence of some Bk+1 if machine is complete. • Reset and Bridge Sequences

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