tdd workshop

A workshop on test-driven development presented during Tryst 2013, an annual science and technology festival at IIT Delhi.

Transcript

1. test-driven development why do cars have brakes?
2. At the end of this workshop... Build production quality software Experience unit testing Appreciate good design principles Gain insights Taking it further
4. “One broken window, left unrepaired for any substantial length of time, instills in the inhabitants of the building a sense of abandonment – a sense that the powers that be don’t care about the building. So another window gets broken. People start littering. Graffiti appears. Serious structural damage begins. In a relatively short space of time, the building becomes damaged beyond the owner’s desire to fix it, and the sense of abandonment becomes reality.” The Pragmatic Programmer
5. “Legacy code is code without tests.” Michael Feathers, 2002
6. code inspection only take you so far...
7. A software development technique in which automated tests are written iteratively alongside the production code TDD
8. A software development technique in which automated tests are written iteratively alongside the production code TDD
9. A software development technique in which automated tests are written iteratively alongside the production code TDD
10. A software development technique in which automated tests are written iteratively alongside the production code TDD
11. “But one should not first make the program and then prove its correctness, because then the requirement of providing the proof would only increase the poor programmer's burden. On the contrary: the programmer should let correctness proof and program grow hand in hand.” The Humble Programmer, Edsger W. Dijkstra 1972
12. No excuses Avoid “we’re too busy” Defer “let QA test the software” Deny “we don’t have bugs” Play dumb “we don’t know how”
13. Three simple rules You can’t write production code unless it makes a failing unit test pass. Rule 1
14. Three simple rules You can’t write any more of unit test that is sufficient to fail, and not compiling is failing. Rule 2
15. Three simple rules You can’t write any more production code than is sufficient to pass one failing unit test. Rule 3
16. the development lifecycle
17. half-adder circuit
18. Core entities Wire Inverter OrGate AndGate Probe
19. Courage Introduce change Refactor Evolve the design
20. Feedback Improves your design Shows how it works Tells you when done
21. TDD doesn't drive good design. TDD gives you immediate feedback about what is likely to be bad design. -Kent Beck
22. Simplicity Clean code Simple design Evolution
23. Communication Documents behavior Reveals intent Tells you when things stop working
24. Good unit tests are... Fast Isolated Repeatable Self-validating Timely
25. “Brakes allow you to travel faster because you have the power to stop.” So why do cars have brakes?
26. suggested reading