System Test Planning and the usefulness of a “Safety Checklist”

1. System Test Planningand the usefulness of a “Safety Checklist” ECEN5033 R. Dameron, University of Colorado, ECEN5033, System Test Planning

2. State Transition Diagram for “split” routine R. Dameron, University of Colorado, ECEN5033, System Test Planning

3. Present State Input or Event Action Output Next State ST1. Idle card inserted request for PIN Waiting for PIN ST2. Waiting for PINPIN entered display asterisks Validating PIN ST3. Waiting for PINcancel display msg Ejecting ST4. Validating PINindicates “valid” display choices Waiting for customer transaction choice ST5. Validating PINindicates “stolen” display “stolen” confiscating ST6. Validating PINindicates “invalid” display “invalid” Waiting for PIN ST7. Waiting for customer transaction choice Cancel display “cancel” Ejecting ST8. Waiting for customer transaction choice Balance Query selected Processing query continued on next slide R. Dameron, University of Colorado, ECEN5033, System Test Planning

4. ST9. Waiting for customer transaction choice Withdrawal selected Processing w/d ST10. confiscating Card confiscated terminating ST11. Processing query Rejected for this user display “rejected” Ejecting ST12. Processing query Query OK display printing printing ST13. Processing withdrawal ok amount display ok msg dispensing ST14. Processing withdrawal not ok amount display refusal Ejecting ST15. Printing transaction complete print receipt ejecting ST16. Dispensing sufficient cash in ATM cash printing ST17. Dispensing insufficient cash in ATM disp “insufficient cash” ejecting ST18. Ejecting card ejection started display msg to take card terminating ST19. terminating card ejection complete display ending msg idle R. Dameron, University of Colorado, ECEN5033, System Test Planning

5. State Transition Diagram - incomplete card inserted/ PIN inserted/ waiting for PIN Idle validating PIN “invalid” card ej complete “cancel” “stolen” ejecting “valid” terminat-ing confis-cating waiting for cust xaction card confis’d “cancel” R. Dameron, University of Colorado, ECEN5033, System Test Planning

6. 2-dimensional event table Action;action = sequential actions. Action, action = concurrent actions. X = impossible. --- = no action required. R. Dameron, University of Colorado, ECEN5033, System Test Planning

7. Checklist regarding Robustness R. Dameron, University of Colorado, ECEN5033, System Test Planning

8. Robustness 11. If performance degradation is the chosen response, is the degradation predictable? 12. Are there sufficient delays incorporated into the error-recovery responses, e.g. don’t return to normal state prior to managing the error 13. Are feedback loops specified where appropriate to compare the actual effects of outputs on the system with the predicted effects? R. Dameron, University of Colorado, ECEN5033, System Test Planning

9. Robustness, continued • Are all modes and modules reachable (used in some path through the code)? Superfluous? Other logic error? • If a hazards analysis has been done, does every path from a hazardous state (a failure-mode) lead to a low-risk state? • Are the inputs identified which, if not received, can lead to a hazardous state or can prevent recovery (single-point failures)? R. Dameron, University of Colorado, ECEN5033, System Test Planning

10. Usefulness? • Safety checklist has been demonstrated to “ask the right questions” • Not sufficient to preclude introducing errors • Necessary although not sufficient R. Dameron, University of Colorado, ECEN5033, System Test Planning

11. #1 #2 #4 May I have the envelope, please … Not every hazardous state led to a low-risk state. Error-recovery responses incorporated insufficient delays. Input arrived when it shouldn’t and no response was specified; response defaulted to unintended behavior. Response not specified for out-of-range values that were possible for some inputs #5 Output produced too fast for interfacing module #3 R. Dameron, University of Colorado, ECEN5033, System Test Planning

12. Allows tailoring • Focuses on historically troublesome aspects of safety-critical, embedded software • Avoids over-specification of well-understood or low-risk requirements • Tailor to level of technical or historical risk R. Dameron, University of Colorado, ECEN5033, System Test Planning

13. First step toward safety constraints • Many items that it identifies are system hazards • Can be used to identify safety constraints • Not yet ready for formal prediction • How use for informal prediction of error prone factors R. Dameron, University of Colorado, ECEN5033, System Test Planning

14. After Requirements Are Improved … • How do we ensure that requirements are implemented and maintained? • After code is written (new code or bug fixes); note: difficult to unit test these issues • After new requirements are added • After old requirements are modified • Role of reviews • Code the invariants where appropriate • System tests to test use cases and the safety checklist R. Dameron, University of Colorado, ECEN5033, System Test Planning

15. Create a system test plan – IEEE Std. 829 • Test the Success Scenario and conditions that lead to alternative paths of use cases • If possible, test to verify the relevant safety checklist items – “safety” may not be main concern but correct interfaces and robustness are. • If any resources are shared among processes, review and test for correctness of mutual exclusion. (SW Eng of Multi-program Sys) • If “cooperating processes”, verify suspension happens correctly, a suspended process restored when appropriate, restoration correct. R. Dameron, University of Colorado, ECEN5033, System Test Planning

16. IEEE 829 Standard Test Plan Outline 1.0 Introduction 2.0 Test Items 3.0 Tested Features 4.0 Features Not Tested (per cycle) 5.0 Testing Strategy and Approach 5.1 Syntax 5.2 Description of functionality 5.3 Arguments for Tests 5.4 Expected Output 5.5 Specific Exclusions 5.6 Dependencies 5.7 Test Case Success/Failure Criteria R. Dameron, University of Colorado, ECEN5033, System Test Planning

17. 1.0 Introduction 2.0 Test Items 3.0 Tested Features 4.0 Features Not Tested (per cycle) [Repeat 5.0 for each system level test.] 5.0 Testing Strategy and Approach 5.1 Syntax 5.2 Description of functionality 5.3 Arguments for Test 5.4 Expected Output 5.5 Specific Exclusions 5.6 Dependencies 5.7 Test Case Success/Failure Criteria IEEE 829 Standard Test Plan Outline - 1 R. Dameron, University of Colorado, ECEN5033, System Test Planning

18. IEEE 829 Standard Test Plan Outline - 2 6.0 Pass/Fail Criteria for the Complete Test Cycle 7.0 Entrance Criteria/Exit Criteria 8.0 Test-Suspension Criteria and Resumption Req’s 9.0 Test Deliverables/Status Communications Vehicles 10.0 Testing Tasks 11.0 Hardware and Software Requirements (for testing) 12.0 Problem Determination and Correction Responsibilities R. Dameron, University of Colorado, ECEN5033, System Test Planning

19. IEEE 829 Standard Test Plan outline - 3 13.0 Staffing and Training Needs/Assignments 14.0 Test Schedules 15.0 Risks and Contingencies 16.0 Approvals R. Dameron, University of Colorado, ECEN5033, System Test Planning

20. Glass-box – briefly (Need implementation details) • Test module/process/object-cluster interfaces (process level can be system test) • Test object/object-cluster contracts • Create test data to force certain code paths • Note: if team is doing incremental development, you can begin glass-box testing early R. Dameron, University of Colorado, ECEN5033, System Test Planning

21. More to consider • If the system is too large to test thoroughly, what tests should you emphasize? • Stay tuned … R. Dameron, University of Colorado, ECEN5033, System Test Planning

22. HAZOP System Safety: HAZOP and Software HAZOP, by Felix Redmill, Morris Chudleigh, James Catmur, John Wiley & Sons, 1999 R. Dameron, University of Colorado, ECEN5033, System Test Planning

23. What is HAZOP? • Technique for identifying and analyzing the hazards and operational concerns of a system. • Central activity – a methodical investigation of a system description (design representation). R. Dameron, University of Colorado, ECEN5033, System Test Planning

24. What this presentation does not cover: • The book puts a LOT of emphasis on • Selecting the study initiator • Selecting the study leader • Planning the study • Roles during the study • Questions vs. follow-up • Completion criteria (P.S. It also tells how to conduct the study itself :-) R. Dameron, University of Colorado, ECEN5033, System Test Planning

25. Reasonable Limits for this class • This is a human-intensive activity • As such, the details on the previous page are of extreme importance – authors are experienced and therefore recognize this • You won’t be able to conduct a HAZOP study on the basis of these slides • Goal: Understand what it is – set the bar higher R. Dameron, University of Colorado, ECEN5033, System Test Planning

26. Study process itself in a nutshell Introductions Presentation of design notation Examine design methodically one unit at a time Is it possible to deviate from design intent here? YES Examine both consequences and causes of the possible deviation NO NO Document results Define follow-up work YES Time up? Agree on documentation R. Dameron, University of Colorado, ECEN5033, System Test Planning Sign off

27. Examine design methodically each unit in turn • Suppose the design representation is a collection of state transition tables: • Units are states, transitions, event/action pairs • For EACH, list the recommended attributes (see table from the Hazop book) • For each attribute, use the guide words to trigger the questions about ways to deviate R. Dameron, University of Colorado, ECEN5033, System Test Planning

28. The suggested guide words • No: negation of design intention; no part of design intention is achieved but nothing else happens • More: Quantitative increase • Less: Quantitative decrease • As well as: Qualitative increase where all design intention is achieved plus additional activity • Part of: Qualitative decrease where only part of the design intention is achieved • Reverse: logical opposite of the intention • Other than: complete substituion, where no part of the original intention is achieved but something quite different happens R. Dameron, University of Colorado, ECEN5033, System Test Planning

29. When timing matters • Add the following guide words: • Early: something happens earlier in time than intended • Late: something happens later in time than intended • Before: something happens earlier in a sequence than intended • After: something happens later in a sequence than intended R. Dameron, University of Colorado, ECEN5033, System Test Planning

30. Guide words chosen • Match the system being examined to appropriate table or modify the closest • Match the design representation • Note: not all guide words apply to all attributes • For attribute “speed” of an electric motor, omit guide word “as well as” and “part of” • For attribute “data flow” on a dfd, “less” is not used because meaning covered by “part of” • Generally, study leader selects from the guide words, provides interpretations based on chosen design representation and context, distributes to team in advance of the study R. Dameron, University of Colorado, ECEN5033, System Test Planning

31. Applications • Originally developed for chemical plants • Book has detailed examples for • Software using data flow diagrams • Software using state transition diagrams • Includes timing attributes of response time and repetition time • Software using various OO models • Digital electronics • Communication systems • Electromechanical systems • Same guide words, different interpretations R. Dameron, University of Colorado, ECEN5033, System Test Planning

32. More detailed outline of the HAZOP process – Figure 9.2 For all entities For all attributes For each guide word Is deviation credible? Example matrices See book excerpts R. Dameron, University of Colorado, ECEN5033, System Test Planning

33. Fig 9.2 HAZOP meeting process R. Dameron, University of Colorado, ECEN5033, System Test Planning

34. R. Dameron, University of Colorado, ECEN5033, System Test Planning