Fundamentals of Software Engineering
- 1. Test Strategies for Conventional Software
- 2. 2 Unit Testing • Focuses testing on the function or software module • Concentrates on the internal processing logic and data structures • Is simplified when a module is designed with high cohesion – Reduces the number of test cases – Allows errors to be more easily predicted and uncovered • Concentrates on critical modules and those with high cyclomatic complexity when testing resources are limited
- 3. 3 Targets for Unit Test Cases • Module interface – Ensure that information flows properly into and out of the module • Local data structures – Ensure that data stored temporarily maintains its integrity during all steps in an algorithm execution • Boundary conditions – Ensure that the module operates properly at boundary values established to limit or restrict processing • Independent paths (basis paths) – Paths are exercised to ensure that all statements in a module have been executed at least once • Error handling paths – Ensure that the algorithms respond correctly to specific error conditions
- 4. 4 Common Computational Errors in Execution Paths • Misunderstood or incorrect arithmetic precedence • Mixed mode operations (e.g., int, float, char) • Incorrect initialization of values • Precision inaccuracy and round-off errors • Incorrect symbolic representation of an expression (int vs. float)
- 5. 5 Other Errors to Uncover • Comparison of different data types • Incorrect logical operators or precedence • Expectation of equality when precision error makes equality unlikely (using == with float types) • Incorrect comparison of variables • Improper or nonexistent loop termination • Failure to exit when divergent iteration is encountered • Improperly modified loop variables • Boundary value violations
- 6. 6 Problems to uncover in Error Handling • Error description is unintelligible or ambiguous • Error noted does not correspond to error encountered • Error condition causes operating system intervention prior to error handling • Exception condition processing is incorrect • Error description does not provide enough information to assist in the location of the cause of the error
- 7. 7 Drivers and Stubs for Unit Testing • Driver – A simple main program that accepts test case data, passes such data to the component being tested, and prints the returned results • Stubs – Serve to replace modules that are subordinate to (called by) the component to be tested – It uses the module’s exact interface, may do minimal data manipulation, provides verification of entry, and returns control to the module undergoing testing • Drivers and stubs both represent overhead – Both must be written but don’t constitute part of the installed software product