• Continue partners!
• Quiz day is food day.

Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
  • Quiz.
• Lab.
• Key ideas in testing.
• Careful postconditions.
• Exhaustive testing.
• Making yourself more efficient.

Preliminaries

Admin

• Mentor session Monday at 7:00 p.m.
• Friday PSA.
• We'll try to to keep quizzes closer to ten minutes today.
• The last fifteen minutes of today's class will be debriefing.
• My life is complicated next week. We have a candidate on campus on Monday and I'm coaching the middle school MATHCOUNTS team all day Tuesday. I'll be available via email, but probably not in person, for a lot of the day.
  (I'll be in my office Monday at 11:00 and at 3:15, but not other times.)

Upcoming Work

• Exam 1.
  • Required prologue due TONIGHT.
  • Exam due in electronic form next Tuesday.
  • Exam due in printed form next Wednesday.
  • Required epilogue due next Wednesday night.
  • You may have an extra day to do the exam because of my limited availability early next week.
• Lab writeup for lab 10, due Monday, Problem 9 http://bit.ly/151-2015S-lab10
• Reading for Monday:
  • Design and Color

Extra Credit Opportunities

Academic

• TEDx Grinnell, sometime in February.

Miscellaneous

• Read and comment on the new Grinnell College Guide to Preventing, Reporting, and Responding to Sexual Harassment and Sexual Misconduct

Peer Support (Afternoon Section)

• Track and Field, Saturday at 10 a.m., the Bear Fieldhouse (800 is the best race)
• Men's Basketball, Saturday at 3:00 p.m., New Darby
• Swimming, Conference Championships, February 13-15, The Osgood

Questions

I've spent twenty minutes on this problem and I'm not making any more progress. Will I get I partial credit?

Ask questions after ten! Ask questions after twenty!

I'm not sure if I can ask you this, but ...

Be sure. You can.

Quiz

• When you finish the quiz, start working on your lab. Your partner will catch up.

Lab

• We'll stop with about fifteen minutes to go so that we can debrief.
• What does test-case do? (test-case "Description of test" statement1 statement2 ... statementn)
  • Evaluate each statement in turn.
  • If any of the statements fails (reports an error), prints the description.
  • If none of the statements reports an error, prints nothing

Key ideas in testing

• Tests need to be broad to catch different perspectives on what a procedure is supposed to do.
• Good postconditions can lead to good tests (and vice versa)
• It's hard to come up with good postconditions and good tests.
• It's nice to be able to look at the code to write tests, so it's even harder because we don't have access to that code.
• Try to write clear tests and clear code.
• If a test fails, it may be an incorrect test rather than incorrect code.
• Think carefully about your tests: You should test for different things.

Careful postconditions

• (drawing-center-x result) = x
• (drawing-center-y result) = y
• You want the same shape that you input. If you started with a square, you want a square. If you strated with a circle, you want a circle.
• You want it the same size/dimensions

Exhaustive testing

• Test shifting left and right and up and down
• Different shapes: circle, squares, non-square rectangles, non-circular ellipses, compound drawings
• Think about edge/corner cases: 0
• Think about weird variants: Negative targets, integer/rational, exact/inexact
• A good test suite is not small.

Making yourself more efficient