I read Test-Driven Development: By Example alone, marking the margins with my thoughts.  In lieu of a book club, I’m taking Kent Beck’s book off my bookshelf and in this blog I’m sharing my thoughts–and the thoughts of those with whom I’ve discussed it.

• The explanation of how subtle duplication can be in code (beginning on page 8 ) was memorable for me.
• A coworker was amazed at the recursion in Part II: it illustrates TDD by test-driven development of a testing framework.
• I never found any errata, but my margin notes indicate the following items confused me:

1. On page 51, the format suggests that these two lines are in the classes Franc and Dollar, when at that point they are still in the class Money:

   static Money franc(int amount);
   static Money dollar(int amount);

2. Page 67 reads, “We can make the bar green in one piece of ugliness” but I think this method in Bank also necessary for the code to compile:

   public void addRate(String from, String to, int rate);

3. Page 103 calls

   TestResult.testStarted()

   but page 106 introduces that method.

• Like David Koontz, I liked Kent Beck’s “Cheap Desk, Nice Chair” red bar pattern on page 140.
• I sometimes encounter teams interested in TDD but not, for example, pair programming or continuous integration. Page 204 contains a quick explanation of the relationship between TDD and other XP practices.
• I really like the influence diagrams in the book and explained in Appendix I. The idea comes from Gerald Weinberg’s Quality Software Management: Systems Thinking.

What comments are in the margins of your copy of Test-Driven Development: By Example?

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