Fix these first embedded systems 7 software

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Unformatted text preview: e to fix all of them – The Pareto Principle defines “the vital few, the trivial many” • Bugs are uneven in frequency – a vital few contribute the majority of the program failures. Fix these first. Embedded Systems 7 Software Development Stages and Testing 1. Planning – – – – System goals: what it will do and why Requirements: what must be done Functional definition: list of features and functionality Testing during Planning: do these make sense? – External design: user’s view of the system • User interface inputs and outputs; System behavior given inputs Internal design: how the system will be implemented • Structural design: how work is divided among pieces of code • Data design: what data the code will work with (data structures) • Logic design: how the code will work (algorithms) Testing during Design • Does the design meet requirements? • Is the design complete? Does it specify how data is passed between modules, what to do in exceptional circumstances, and what starting states should be? • How well does the design support error handling? Are all remotely plausible errors handled? Are errors handled at the appropriate level in the design? 2. Design – – Embedded Systems 8 Software Development Stages 3. Coding and Documentation – Good practices interleave documentation and testing with coding • Document the function as you write it, or once you finish it • Test the function as you build it. More on this later 4. Black Box Testing and Fixing – After coding is “finished” the testing group beats on the code, sends bug reports to developers. Repeat. 5. Post-Release Maintenance and Enhancement • 42% of total software development budget spent on userrequested enhancements • 25% adapting program to work with new hardware or other programs • 20% fixing errors • 6% fixing documentation • 4% improving performance Embedded Systems 9 Development and Testing Approach: Incremental vs. Big Bang Testing Incremental Testing – Code a function and then test it (module/unit/element testing) – Then test a few working functions together (integration testing) • Continue enlarging the scope of tests as you write new functions – Incremental testing requires extra code for the test harness • A driver function calls the function to be tested • A stub function might be needed to simulate a function called by the function under test, and which returns or modifies data. • The test harness can automate the testing of individual functions to detect later bugs Big Bang Testing – Code up all of the functions to create the system – Test the complete system • Plug and pray Embedded Systems 10 Why Test Incrementally? Finding out what failed is much easier – With BB, since no function has been thoroughly...
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