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Software testing day1

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Software testing day1

  1. 1. Software Testing Van Thi Kim Ngan Aug-2005
  2. 2. Agenda • • • • • What is test? Why is testing necessary? What is bug? Lifecycle of a bug Record and Manage bug
  3. 3. What is test? • Testing is the process of exercising or evaluating a system or system component by manual or automated means to verify that it satisfies specified requirements
  4. 4. Some English… • Verification : Methods to ensure that the system complies with an organizational standard or process • Validation: Ensure that the system operates according to a plan by executing system functions
  5. 5. Why is testing necessary? • Because software is likely to have faults • To learn about the reliability of the software • Because failures can be very expensive • To avoid being sued by customers • To stay in business
  6. 6. What is bug? • A fault in a program which causes the program to perform in an unintended or unanticipated manner.
  7. 7. Failure • Deviation of the software from its expected delivery or service • Failure is an event
  8. 8. Fault • Cause that failure is caused • Defect or error inside a program It is said to be a bug generally
  9. 9. Error • A human action that produces an incorrect result Mistake Oversight Hand omission
  10. 10. Relation of failure, fault and error A person makes an error ... … that creates a fault in the software ... … that can cause a failure in operation
  11. 11. “Importance” of bugs (in $$) • Frequency (Fre) • Correction cost (Cor): – Typically, significantly more the later the bug is discovered • Installation cost (Ins): – Cost of installing the fix • Consequences (Con)
  12. 12. “Importance” of bugs (Con.) • Importance = Fre * (Cor + Ins + Con) – It’s not obvious that these costs can simply be added. – Another cost item may be “bug maintenance”: help desk effort, etc., to assist users to work around it
  13. 13. Cost of bugs
  14. 14. Bug Lifecycle LOG DEFECT Defect status: ERROR Analyse Defect ASSIGN DEFECT Defect status: ASSIGNED CORRECT DEFECT Defect status: PENDING Error Retest Defect Corrected CLOSE DEFECT Defect status: TESTED ACCEPT DEFECT Defect status: ACCEPTED
  15. 15. Not all bugs are equal Fatal Damage Serious Medium Cosmetic Bug Type
  16. 16. Bug severity • Cosmetic bugs – A defect that in no way affects the performance of the product. It may be a grammatical error • Medium bugs – This defect doesn’t stop the user from proceeding, but causes inconvenience
  17. 17. Bug severity (Con.) • Serious bugs – System cannot work around • Fatal bugs – Defects may stop the user from using the system further, the system is crashed
  18. 18. Bug Status • ERROR – The defect is not fixed, or fixed but not satisfactorily as required • ASSIGNED – The defect is reviewed and assigned to fix it • PENDING – The defect is already fixed and waiting to retest
  19. 19. Bug Status (Con.) • TESTED – The defect is fixed satisfactorily as required • ACCEPTED – The defect has not been fixed satisfactorily as required, but it’s accepted by concession of authority or customer • CANCELLED – It’s not a defect or defect is removed by actions other than bug fixing
  20. 20. Bug classification • • • • • • Requirements and feature bugs Structural bugs Data bugs Coding bugs Interface, integration and system bugs Test and test design bugs
  21. 21. Bug classification (Con.) • Requirements & Feature Bugs – Requirements bugs are the first to invade the system and the last to leave – Specs are often self-contradictory, incomplete and ambiguous – Extra features, other gratuitous enhancements tend to be error prone – Feature interaction problems
  22. 22. Bug classification (Con.) • Structural Bugs – – – – Control and sequence bugs Logic bugs Processing bugs Initialization and dataflow bugs
  23. 23. Bug classification (Con.) • Structure & Sequence Bugs – – – – Unreachable code Paths left out Goto problems Spaghetti code
  24. 24. Bug classification (Con.) • Logic Bugs – – – – Misunderstood switch-statement semantics Improper Boolean logic Improper simplification and combination of cases Misunderstood expression evaluation
  25. 25. Bug classification (Con.) • Processing Bugs – – – Arithmetic bugs Algebraic bugs Incorrect conversion
  26. 26. Bug classification (Con.) • Initialization and data bugs – – – – – Improper initialization Using an un-initialized variable Double initialization Modifying data but not keeping the result Dangling pointers
  27. 27. Bug classification (Con.) • Coding Bugs – – – Typos Misunderstood language syntax and semantics Erroneous comments
  28. 28. Bug classification (Con.) • Interface, Integration & System Bugs – – – External interfaces Internal interfaces Bugs related to hardware, system software, or OS interface – Integration bugs
  29. 29. Bug classification (Con.) • Tests & Test Design Bugs – – Bugs in the test (“scaffolding”) software Bugs in test data
  30. 30. Bug Tracking Tools • Trakium: Issue Tracking System – – Vendor: Multitech www.trakium.com • Test Director: Provide -Requirements Management, Test Plan, Test Case, and Defects Management – – Vendor: Mercury www.mercury.com
  31. 31. Questions & Answers