Test Driven Development

• One of the central ideas from Agile Software Methodology
• But it has been applied too dogmatically
• All your code should be covered by tests
• But not all of it needs to be developed via test-driven-development

What is it?

• It is always done with as an extension to automated testing
• Core idea: write the tests before you write the code
• Sounds counter-intuitive!
  • Allows you to think of making your API clean before you worry about how to implement it
  • Allows you to build up your functionality with confidence of a solid foundation
  • Prepares you to be able to introduce refactoring with confidence

Money Demo

• Goal: A Money class
  • represent money in different currencies
  • What are all the operations you would want to do with them?
  • As a client how do you want to call them?
  • Discuss with a neighbor how you would write the test