Lean Code

A workshop run at conferences and user groups which helps people understand how the constraints of delivery and changing requirements affects their code.

Transcript

1. The Lean Code Challenge Sit in pairs: at least one will need a laptop. You’ll be reading from stdin and writing to stdout. Find someone who knows the same language as you! Thursday, 12 July 12
2. What is Lean? Thursday, 12 July 12
3. Lean software development Thursday, 12 July 12
4. Eliminate Waste Thursday, 12 July 12
5. Focus on Value Thursday, 12 July 12
6. Deliver Fast Thursday, 12 July 12
7. Decide Late Thursday, 12 July 12
8. Can code be lean? Thursday, 12 July 12
9. Introducing the customer Thursday, 12 July 12
10. Fresco plc Thursday, 12 July 12
11. Iteration 0 10 minutes to choose a pair, and set up your dev environment We are writing a command line tool: accept stdin, write stdout. If you need a quick environment in Ruby: $ git clone git://github.com/chrismdp/checkout-kata.git $ git checkout lean_code_start $ bin/checkout Thursday, 12 July 12
12. Iteration 1 10 minutes to write a simple checkout scanner • Apples cost £1, Bananas cost £1.50, Cherries cost £0.75 • Accept each of these words one per line on stdin • Print the cart total in pence on stdout each time. • Questions? Acceptance Test: • Apples => 100 • Cherries => 175 • Cherries => 250 Thursday, 12 July 12
13. Iteration 2 10 minutes to add a discount: • Same input and output as before • Two lots of Cherries get 20p off. Acceptance test: • Apples => 100 • Cherries => 175 • Cherries => 230 Thursday, 12 July 12
14. Iteration 3 10 minutes to add CSV format: • Now need to accept the values as comma seperated • Same prices as Iteration 2 Acceptance test: • Apples, Cherries, Bananas => 325 • Cherries, Cherries => 130 Thursday, 12 July 12
15. Iteration 3a No! Urgent requirement from business! Deadline the same. • Fresco suppliers notified delay of new API requiring CSV • Now input back to one per line • Cherries have now got 30p discount • Bananas are now Buy One Get One Free Acceptance test: • Cherries => 75 • Cherries => 120 • Bananas => 270 • Bananas => 270 Thursday, 12 July 12
16. Iteration 4 10 minutes to support localisation: • Fresco suppliers still behind on CSV change • Cherries are now back to 20p discount • Should also support the words “Pommes” and “Mele” for apples. Acceptance test: • Cherries => 75 • Pommes => 175 • Cherries => 230 • Bananas => 380 • Bananas => 380 • Apples => 480 Thursday, 12 July 12
17. Iteration 5 10 minutes to support seperate discounts for different names: • Be advised CSV change is coming next iteration • 3 x Pommes is discounted to £2 • 2 x Mela is discounted to £1.50 Acceptance test: • Mele => 100 • Pommes => 200 • Pommes => 300 • Apples => 400 • Pommes => 400 • Mele => 450 • Cherries => 525 • Cherries => 580 Thursday, 12 July 12
18. Iteration 5a 10 minutes to support seperate discounts for different names: • NEW TILLS DEPLOYED YOUR CODE IS BROKEN! • 3 x Pommes is discounted to £2 • 2 x Mela is discounted to £1 Acceptance test: • Mele, Pommes, Pommes, Apples, Pommes, Mele, Cherries, Cherries, Bananas => 680 Thursday, 12 July 12
19. Iteration 6 10 minutes to work around supplier bug and apply super- discount: • Supplier bug: support entry of both CR seperated and CSV • 2 x Mele is discounted to £1.50 • Buy 4 apples and get another £1 off the bill. • Buy 5 pieces of Fruit a get a further £2 off the bill. Acceptance test: • Mele, Pommes, Pommes, Mele => 250 • Bananas => 200 Acceptance test: • Mele, Pommes, Pommes, Apples, Mele => 150 Thursday, 12 July 12
20. Conclusions Thursday, 12 July 12
21. Eliminate Waste Thursday, 12 July 12
22. Focus on Value Thursday, 12 July 12
23. Deliver Fast Thursday, 12 July 12
24. Decide Late Thursday, 12 July 12
25. “The quality of your software is inversely proportional to how often you have to say no to your customer.” -- Uncle Bob Martin Thursday, 12 July 12
26. git clone git://github.com/chrismdp/checkout-kata.git git checkout lean_code Thursday, 12 July 12