Held: ,

Back to Outline 07 - Codes of Ethics. On to Outline 09 - Pause for Breah .

Summary

We consider issues in writing correct code, particularly test-driven development and ways to identify code that is likely to have errors.

Related Pages

• http://martinfowler.com/bliki/CodeSmell.html

Overview

• Review: Buggy code.
• Loop invariants.
• Code smells.
• Test-driven development.
• Code coverage.
• Work time.

Administrivia

• Welcome back! I hope you had a good break.
• Most of you seem to have done the reading journals for this week, but not necessarily the programming assignment. We'll probably use the second half of class for you to make progress on the programming assignment.
• I don't seem to have the second half of the course up yet; I'm waiting for the folks at EdX to post it.
  
  • Reading: Chapter 5.
  • Programming: https://github.com/saasbook/hw-oracle-of-bacon
  • Partners tonight.

Refresher: Incorrect code

What does this program try to do?

class TimeSetter
  def self.convert(d)
    y = 1980
    while (d > 365) do
      if ((y % 400 == 0) || (y % 4 == 0) && (y % 100 != 0))
        if (d > 366)
          d -= 366
          y += 1
        end
      else
        d -= 365
        y += 1
      end
    end
  end
end

What is wrong with this program?

How would we find it?

How would we fix it?

Loop invariants

• The CSC207 part of my brain wants you to fix this with loop invariants.
• So let's remember what loop invariants are. Three main aspects.
• How would the help with this program?

Code smells

• What are they?
• Why do we care?
• What are some useful smells to look for?
  • SOFA (or the inverse thereof - LMMC)
• What are smells that you look for?
• How do we make things smell better?

Unit testing

• Why?
• How?
• Your notes:
  • Tests first, rather than code first.
  • Make tests independent.
  • Code to test ratio vs. code coverage
  • stubs vs. mocks vs ....

Code Coverage

• Basically: How much of the code that we've written actually gets touched by our tests.