Approaches to ---Testing Software

1. Approaches to ---Testing Software • Some of us “hope” that our software works as opposed to “ensuring” that our software works? Why? • Just foolish • Lazy • Believe that its too costly (time, resource, effort, etc.) • Lack of knowledge • DO NOT use the “I feel lucky” or “I feel confident” approach to testing - - - - although you may feel that way sometimes. • Use a methodical approach to testing to back up the “I feel ‘lucky/confident” feeling • Methods and metrics utilized must show VALUE • Value, unfortunately, often are expressed in negative terms • Severe problems that cost loss of lives or business • Problems that cost more than testing expenses and effort

2. Demonstrate Value of Testing • Catastrophic problems (e.g. life or business ending ones) do not need any measurements---but--- others do: • Measure the cost of problems found by customers • Cost of problem reporting/recording • Cost of problem recreation • Cost of problem fix and retest • Cost of solution packaging and distribution • Cost of managing the customer problem-to-resolution steps • Measure the cost of discovering the problems and fixing them prior to release • Cost of planning reviews and testing • Cost of executing reviews and testing • Cost of fixing the problems found and retest • Cost of inserting fixes and updates • Cost of managing problem-to-resolution steps • Compare the two costs & include loss of customer “good-will”

3. Conflicting Beliefs about Software • Software development is an art: • It takes artistic creativity to develop a competitive software; thus rigorous, repeatable techniques and testing is not needed. • This is pure garbage --- great artist go through and master very rigorous training in techniques and basics before they create their own material • Software development is science and engineering: • It takes system science and engineering to develop competitive and good quality software; thus creativity and artistic notions are irrelevant. • This is also pure garbage - - - “great” & “competitive” scientific and engineering products require innovation and artistic creativity • You NEED Both ! • Need innovation and experimentation • There are potentially too large a set of logical combinations • Repeatability and consistency • Good measurements and records must be kept

4. Need an “Engineering” Approach • Calling “programmers” and “testers” software engineers do not make them engineers. • Engineers apply science to their problem solving • Apply science to finding and resolving “bugs” • Plan for test (what activities, when and whom) • Devise test scenarios and test cases • Apply measurement and keep track of results • Fundamental rules for practicing engineering include: • Stating the methods followed and why • State the assumptions • Apply adequate factors of safety • Get a second opinion “where reasonable” (Not “always” as the book states)

5. Engineering Practices • Stating the methods used and why • Clearly define the methodology and perform accordingly (SEI & ISO) • (Try defining a methodology that describes test planning) • State all the assumptions • List the unknowns and dependencies (there are many in complex systems) • Examples for testing are: • What types of testing (functional, regression, etc.) • Operating environments included (db’s, networks, operating systems) • Test process and developers commitments • (any other example?) • Apply “adequate” factor of safety • For a system purported to handle x transactions/second, how much extra “buffer” would/should you be testing for? • Exactly x or 2x? • For testing efforts that took y people-time units before, would you use y or 1.2 y people-units? • Get a second Opinion • Inspections and reviews of test plans, test cases, tests results are very useful • Working “with” external parties to testing, such as development, is important: • Breaking “their” product or • Showing “their” product works to specification

6. Balancing Art and Science in Testing • When organizing and coordinating testing efforts, ---- utilize a lot of “communications” skills • Testing requires a “team” effort • Among testers • Among testing and other software development members • When planning, tracking, and reporting testing, ----- utilize a lot of tools and measurements skills from engineering • Testing is part of a process (e.g. design inspection, unit testing, functional testing, system testing) that requires • Tools (such as ?) • Measurements (such as?) • Testing do not always have to be (preferred though) experts in the application but: • Must use a systematic methodology and sound reasoning (explain?)

7. Bottom-up & Top-Down Testing Approaches • Bottom-up testing approach • Testing the individual pieces (via unit testing) • Combine the tested pieces and test --- continue until the whole is tested • Advantage : methodical and easy to pinpoint problems • Disadvantage: time consuming and integration problem detected late • Top-down testing approach • Bringing the completed the pieces and start testing the complete system • Integrating the new pieces as they are completed and continue the system test • Advantage: see the unexpected integration problem early • Disadvantage: harder to trouble shoot individually, badly tested pieces Author’s assumption of unit tested code on page 66 is a dangerous one! Why? What’s the definition of unit tested code? Who defined it?

8. Black Box and White Box Testing Approaches • Black box testing: • Looking at and the testing the system from the requirements perspective: outside-in • Do not look at the implementation • White box testing: • Looking at and testing the internals of the system and the code structures: inside –out • Develop test cases from the code structure • White box tests requirements but may miss extra material in the code while Black box tests what’s in the code but may miss non-implemented, but required functions

9. Comment on Author’s View (p.67) • “Interested in the Whole system, not any particular part” ------ agree? (yes, but what about helping in problem diagnosis and team play?) • “System is not a finite state machine” --- agree? (it may be a very large finite state machine --- that’s why we use bottom-up and slower process sometimes!) • “Do not know any company who would pay and use different groups of experts to test interface, unit, function, system, etc.” ---- agree? (many do, including MAPICS and IBM.)

10. Test Organization • Independent test group reporting to the same management as the development and the operations (or user) groups. • As part of the development organization • No formal test group and use temporarily formed group • As a part of the operations (or user) organization Advantage & Disadvantage of each proposed test organizational approach?

11. Need Multiple Views & Approaches • We need to consider all the approaches depending on the situation • Values of testing • Scientific/engineering and artistic views • Top-down and bottom-up • Black box & white box • Test organizations • Key is to determine what the goals of your testing are and then plan an approach or approaches that will achieve that goal

12. Goals of Testing? • Test as much as time allows us • Execute as many test cases as time allows? • Validate all the “key” areas • Test only the designated “key”requirements? • Find as much problems as possible • Test all the likely error prone areas and maximize test problems found? • Validate the requirements • Test all the requirements? State your goal(s) for testing. - - - what would you like people to say about your system ?