Brian On Software

As I was reading a couple of ObjectMentor’s blog posts, one of them caught my attention.  It was Tim Ottinger’s post on “TDD on Three Index Cards“.  He recalls how someone missed part of a class he was teaching on TDD and told that individual the fundamental essence of TDD on three index cards in less than 15 minutes.  After reading that, I got myself thinking “Hhhmm…not a bad idea! I wonder if it’s physically possible?“. 

Ten minutes later, I’m at Staples buying some index cards and a couple of markers (for pictures purposes…of course…).  Here’s the final product which every credit goes to Tim for this very simple, practical and useful idea.  Kudos to my wife for taking the pictures.

Here’s a recap of the main ideas behind TDD (full credits goes to Tim):

Card #1. Uncle Bob’s Three Laws

• Write no production code except to pass a failing test.
• Write only enough of a test to demonstrate a failure.
• Write only enough production code to pass the test.

 

Card #2: FIRST Principles

• Fast: Mind-numbingly fast, as in hundreds or thousands per second.
• Isolated: The test isolates a fault clearly.
• Repeatable: I can run it repeatedly and it will pass or fail the same way each time.
• Self-verifying: The Test is unambiguously pass-fail.
• Timely: Produced in lockstep with tiny code changes.

Card #3: Core of TDD

• Red: test fails
• Green: test passes
• Refactor: clean code and tests

By the way, if you’re in the Montreal/Quebec sector and you’d like (or perhaps your team) to know more about TDD (unit testing best practices, patterns of unit testing, introduction to Mock Objects, etc.), I highly recommend taking the two-day Test-Driven Development in .NET training course with us at the CRIM.