behaviour of the called component which are incorrect Timing errors The called

Behaviour of the called component which are incorrect

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behaviour of the called component which are incorrect Timing errors The called and the calling component operate at different speeds and out-of-date information is accessed ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 42 Interface testing guidelines Design tests so that parameters to a called procedure are at the extreme ends of their ranges Always test pointer parameters with null pointers Design tests which cause the component to fail Use stress testing in message passing systems In shared memory systems, vary the order in which components are activated
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©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 43 Stress testing Exercises the system beyond its maximum design load. Stressing the system often causes defects to come to light Stressing the system test failure behaviour.. Systems should not fail catastrophically. Stress testing checks for unacceptable loss of service or data Particularly relevant to distributed systems which can exhibit severe degradation as a network becomes overloaded ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 44 The components to be tested are object classes that are instantiated as objects Larger grain than individual functions so approaches to white-box testing have to be extended No obvious top to the system for top-down integration and testing Object-oriented testing ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 45 Testing levels Testing operations associated with objects Testing object classes Testing clusters of cooperating objects Testing the complete OO system ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 46 Object class testing Complete test coverage of a class involves Testing all operations associated with an object Setting and interrogating all object attributes Exercising the object in all possible states Inheritance makes it more difficult to design object class tests as the information to be tested is not localised ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 47 Weather station object interface Test cases are needed for all operations Use a state model to identify state transitions for testing Examples of testing sequences Shutdown Waiting Shutdown Waiting Calibrating Testing Transmitting Waiting Waiting Collecting Waiting Summarising Transmitting Waiting identifier reportWeather () calibrate (instruments) test () startup (instruments) shutdown (instruments) WeatherStation ©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 48 Object integration Levels of integration are less distinct in object- oriented systems Cluster testing is concerned with integrating and testing clusters of cooperating objects Identify clusters using knowledge of the operation of objects and the system features that are implemented by these clusters
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©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 20 Slide 49 Approaches to cluster testing Use-case or scenario testing Testing is based on a user interactions with the system Has the advantage that it tests system features as experienced by users Thread testing
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