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Debugging Demystified: November 2011 ScratchEd Webinar

Mitch Resnick and Karen Brennan discuss strategies and demonstrate real debugging challenges.

In the November 2011 ScratchEd webinar (recording below), Mitch Resnick and Karen Brennan discussed debugging strategies and shared experiences from their own debugging practices as well as those gathered from other members of the Scratch Team.

Three main classes of debugging strategies were discussed:
Strategy #1: Don’t make the problem.

  • Be incremental.
  • Test as you go. 

Stragegy #2: Fix the problem.

  • Debugging is fun!
  • Be patient.
  • Break it down.
  • Experiment with the code.
  • Get help.
  • Take breaks.

Strategy #2: Fix the problem. (Scratch strategies!)

  • Click on a stack.
  • Visualize with the say block.
  • Single step.
  • Annotate code with comments.
  • Print out scripts to see them side by side.
  • Post to All About Scratch.

Strategy #3: Change your goal.

After the discussion, Karen challenged Mitch to debug three Scratch projects in real-time with help and suggestions from webinar participants: (accompanying Scratch projects are attached below)
Bug #1: Aquarium

  • "One of my fish isn’t swimming right!"

Bug #2: Space Invaders

  • "I am new to Scratch and stuck building a space invaders game. The ship works and can fire at a sprite. But when it hits the sprite nothing happens. I have tried more than one solution without any luck so far. Any advise would be great."

Bug #3: Thanksgiving Game

  • "I made this for my programming class. Problem is though, is when the turkey sprites are suppose to follow the mouse pointer until they reach the destination (table) or hit one of the sides (black lines) the script should restart. Instead of even following the mouse pointer, right when the numbers count down and the game should start, instantly the game screen disappears and it goes back to the interface. Like I said before, it should ONLY do this when a black line or the table is touched. Can you tell me what I did wrong?"  

Attached below are the presentation slides and Scratch projects from the webinar.

We'd love to keep the conversation going! How do you support students' debugging practices? What challenges do you see them experiencing while learning how to debug? Please share your comments or other feedback below.

See you at the next webinar