Design Verification

Design Verification

1. How to verify the correctness of your programs?

2. As a program's logic becomes more complex, it is increasingly important to verify its correctness

3. SELECTING VERIFICATION METHODS

   • DEFECT PROFILE
     • Defect experience
     • Focus on those areas that cause you the most trouble.
   • VERIFICATION EFFECTIVENESS
     • You should identify a family of effective verification techniques
       • Make a practice of using them
   • VERIFICATION ECONOMICS
     • You must learn which verification method work best for you and the conditions under which they work.

4. DESIGN STANDARDS

   • PRODUCT CONVENTIONS
     • Essential if multiple developers are to produce a system that has any external coherence
       • User Interfaces
       • External naming
       • System error handling
       • Installation procedures
       • Help facilities
   • PRODUCT DESIGN STANDARDS
     • Calling and naming conventions
     • Header standards
     • Test standards
     • Documentation formats
   • REUSE STANDARDS
     • They must be properly managed
       • Think about reuse during design / design reviews
     • They can substantially improve your productivity

5. VERIFICATION METHODS

   • SYMBOLIC EXECUTION
     • It covers all symbolic values rather than merely a few tested cases
     • Provides a structured and theoretically sound way to logically verify programs
   • PROOF BY INDUCTION
     • Applies to logical expressions with integer parameters.
     • You start by showing that the logic of a program is true for a base case

6. VERIFYING THE OBJECT STATE MACHINE

   • Check for hidden traps or loops
   • Check for all possible states
   • Check for state orthogonality
   • Check for complete transitions

7. PROGRAM TRACING

   • EXECUTION TABLES
     • Provides an orderly way to check the logic flow in a Logic Specification Template
       • You list the logic steps in order together with the variable and parameters values for each case to be examined.
         • When loops are encountered, their instructions are repeated until the cycle is completed.
     • Time consuming
       • Reliable
         • Simple
   • TRACE TABLES
     • More efficient for verifying logic correctness
       • Involves three complementary techniques:
         • Symbolic Execution
         • Trace table examination of all possible cases
         • Proof by induction

8. VERIFYING PROGRAM CORRECTNESS

   • TESTING LOOPS
     • For-loop Verification
     • While-loop Verification
     • Repeat-until Verification

9. COMMENTS ON VERIFICATION METHODS

   • DESIGN VERIFICATION STRATEGY
     • You should design down and verify up.
   • SPECIFICATION CONFORMANCE
     • Consider all possible logic cases and verify that they're correctly handled.
   • VERIFICATION COMPLEXITY
     • Track the time verification takes and the degree to which it helps you to find design defects
   • FORMAL VERIFICATION METHODS
     • Best used during program design.
     • Human-intensive, subject to error.
     • You must practice each method until you're reasonably proficient.

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