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System testing


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Testing Methods for systems

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System testing

  1. 1. 1 System Testing Bernie Fishpool Testing Methodologies
  2. 2. 2 Strategies  Top down  Skeleton of system is completed  Individual models replaced by stubs displaying messages  As modules completed they are embedded into the system skeleton and tested
  3. 3. 3 Strategies  Bottom up  Individual modules tested in a stand-alone fashion  Individual modules combined into larger units and tested together  Full system test
  4. 4. 4 Planning Testing  Good testing requires:  A thorough knowledge and understanding of what the system is supposed to do  Preparation of ‘expected results’ to be used in testing activities  Identification of system limits  Creation of test data
  5. 5. 5 Objectives of testing  Does the logic work properly?  Does the system work as intended?  Can system be made to crash?  Is all necessary logic present?  Is any functionality missing?  Does system do everything specified?
  6. 6. 6 Functional Testing (Black Box Testing)  Carried out independently of the system  Involves looking at the systems specification and creating test data that covers all inputs and outputs of the function
  7. 7. 7 Logical Testing (White Box Testing)  Testing the logic of the system  Involves studying the system to attempt to test each logic path at least once  e.g. Testing an IF statement in a program or testing validation rule in a database
  8. 8. 8 Problems  Black box testing does not test all logical paths in a system unless sufficient test data is created (which is often not easy to identify)  White box testing does not detect missing functions because you can not test what is not there!
  9. 9. 9 Whole System Testing  WARNING! Testing may take up to as much as 50% of development time
  10. 10. 10 Test Plan You should consider: Purpose of test Objectives and what part of system is being tested Location and timing Where and when
  11. 11. 11 Test description What the inputs are and what the expected outputs are Test procedure How test data is prepared How output results will be captured How results will be analysed Test Plan
  12. 12. 12 Testing for Recovery  Test to ensure that system can recover from various types of failure  This is important in real-time systems controlling physical devices or in large on-line databases  Simulation of hardware and power failures
  13. 13. 13 Testing for Performance  Testing that system can handle volumes of data expected in user environment
  14. 14. 14 Test Data  3 categories of test data  Normal data defined as most general data that the system was designed to handle  Extreme data defined as valid data tested at upper and lower limits of acceptability (boundary testing)  Exceptional data defined as data which the system is capable of detecting and rejecting
  15. 15. 15 Designing Test Data  Live data testing  Tester selects examples of live data from the system which fulfil the conditions to be tested  Manual calculations are undertaken  Results compared
  16. 16. 16 Designing Test Data  Historical data  Sampling of transactions that have already taken place  These transactions are then passed through the system  Results compared
  17. 17. 17 Designing Test Data  Dummy test data  Fictitious data created to test conditions  Creation of dummy files specifically for testing purposes  Useful for:  Validating data preparation procedures  Validation controls  Computational and logical processes
  18. 18. 18 Ensure that:  All system outputs are tested  Information produced is accurate  Information produced is realistic and has value