1. Live TDD Demo
Arithmetic Expression Evaluator
Ionut G. Stan & Andrei Savu

3. Mindset change
Think about the smallest feature that you want to
implement and express it in test code.
Implement it.
This leads to emergent design.

4. Problem
1 + 2 * 5 - 4 = ?
Tools
Python, unittest, TextMate
Data Flow
Expression > Split in tokens > Postfix notation > Evaluate
1+2*5-4 > (1, +, 2, *, 5, -, 4) > (1, 2, 5, *, +, 4, -) > 7

5. Postfix Notation !?
1 + 2 > 1 2 +
1 + 2 - 3 > 1 2 + 3 -
1 + 2 * 3 > 1 2 3 * +
1 + 2 * 3 - 4 > 1 2 3 * + 4 -

6. Conclusions
TDD is no silver bullet

7. Questions?
thanks :)