Cleanroom Software Engineering - Design Refinement and Cleanroom Testing

Design Refinement & Verification
- If a function f is expanded into a sequence g and h, the correctness condition for all input to f is:
• Does g followed by h do f?
When a function f is refined into a conditional (if-then-else), the correctness condition for all input to f is:
• Whenever condition is true does g do f and whenever is false, does h do f?
- When function f is refined as a loop, the correctness conditions for all inputs to f are:
• Is termination guaranteed?
• Whenever is true does g followed by f do f, and whenever is false, does skipping the loop still do f?

Advantages of Design Verification :
- It reduces verification to a finite process.
- It lets cleanroom teams verify every line of design and code.
- It results in a near zero defect level.
- It scales up.
- It produces better code than unit testing.

CLEANROOM TESTING :
The strategy and tactics of cleanroom testing are fundamentally different from conventional testing approaches.
Statistical Testing
- Generation of test cases
* each test case begins in a start state and represents a random walk through the usage model ending at a designated end state.
- Control of statistical testing
* a well-defined procedure is performed under specified conditions.
* each performance is a trial and can be used as part of an empirical probability computation.
- Stopping criteria for testing
* when testing goals or quality standards are achieved.
* when the difference between the predicted usage chain and the actual testing chain becomes very small.