U4: Debugging and Validating Data

• Good for programming as cost of failure is low • Takes little time and money, low stakes

• Trial and error cheaper in earlier stages of Software Development Life Cycle • Error costs x10 more to fix at each next stage

Continually trying solutions, refining each one, getting closer to end goal

• Occurs when program crashes • Can be caused by dividing by 0, opening nonexistent file

• Mistake in writing code • Ex: Missing variable, forgetting curly bracket • AKA: Compile Time Errors as they’re caught while compiling

• Program runs but output incorrect • Can cause run-time error as well

Solution where problem broken down into smaller and smaller sub-problems until each can be solved in few steps

Visualizers inspect values of objects

Allow to see how code executes step by step

Visualizers include tools for visualizing data structures (ex: arrays, lists, trees, graphs).

• Outputting values of variables during program • Delete output statements when program debugged

• Should have wide range of input data • Include different data (ex: 0, decimals instead of strings)

• Includes aspects of program tested • Outcomes of test (positive or negative and details to errors) • Changes made to program

Checking to ensure data entered is expected

• “try” command tries algorithm that may cause crash • “catch” command catches problem, stopping catch