1. Teaching A Goliath to Fly
Why Goliath
Why Fly
Salim Nair
Prasad Ramnath
Agile Development Conference 2005
Denver, Colorado

2. The good stuff first
This is a story of applying agile practices in a large legacy code base. Here are the lessons we learnt
Refactoring legacy code cannot work in isolation
Legacy code is not bad code; just legacy code
Refactor just enough to put your feature under test.
Follow simple architectural principles
Agile development in a legacy framework can only work by evolution.
Start refactoring bottom-up, followed by a periodic top-down review to unify the architecture
Salim
Prasad

3. Some background About Primavera Systems
Primavera is the largest independent provider of collaborative project, resource and portfolio management solutions.
20 year progress through technology
Began with project management tools developed in DOS
Currently has a large application suite for enterprise project, portfolio and resource management comprised of several applications written in Delphi and Java, client-server to J2EE
This paper talks about transforming the Delphi Codebase (1.5 M lines) to enable agile development
Prasad
Salim

4. Where were we… Traditional waterfall development
Requirements handed out in the beginning of the release cycle
Isolated development where each programmer is assigned a feature
Long release cycles with typical ping-pong game between testers and programmers
Long work hours during last several months of the release cycle to finish up the features
Salim – 1-2
Prasad – 3-4

5. Where were we… 1.5 M lines of code in Delphi, starting from Delphi 1.0
Runaway dependencies due to implicit includes
Conditional compiler directives to create individual applications
Event-driven programming model

6. Where are we… Introduction of Scrum in 2003
10-15 cross-functional teams
Test Driven Development in 2004
Bob and Micah Martin, Michael Feathers
Finally facing up to the Goliath
1-3 Prasad
4-5 Salim

7. Lesson 1 Refactoring legacy code cannot work in isolation
Restating core agile principle
Unity project – story of a brave man facing the challenges alone!!!
“Lets rewrite this thing in parallel” – story of an ever missing train
Prasad

8. Path to lesson 2: Refactor “Bad” code
Task Calendar Mgr, the God Class
Unit testing legacy code
Salim
Using interfaces for refactoring VirtualRow

9. Lesson 2 Legacy code is not bad code; just legacy code
Tried to refactor legacy framework just because it was there
Struggling with TDD
Refactoring large legacy classes
Prasad

10. Lesson 3 The epiphany: TDD the feature, not the legacy code
Refactor just enough to write your test
The epiphany:
It is better to be simplistic
All Animesh cared was how to write test for his feature!!!
TDD the feature, not the legacy code
If you feel the pain, change it. But, don’t be masochists
Prasad – 1, 3
Salim – 2

11. Birth of Business Object Framework

12. Lesson 4
When you don’t know better, follow simple architectural principles
Single responsibility
Controlled linear dependencies
Testability
Salim – 1-2
Prasad - 3

13. Lesson 5 Each team contributed to BOF for their specific feature
Agile development in a legacy framework can only work by evolution.
Each team contributed to BOF for their specific feature
Divide and conquer
Evolve fully tested parallel frameworks to replace existing ones when needed
Salim – 1, 3, 5
Prasad – 2, 3
Create formal ways to control dependency

14. Lesson 6 Incremental evolution and discrepancies
Start refactoring bottom-up, followed by a periodic top-down review to unify the architecture
Incremental evolution and discrepancies
Finding patterns and emerging architecture
Mentoring to conform
Review and refactor
Have a vision
Prasad – 1- 3
Salim – 4-5

15. Where will we be… 100% of new features developed using TDD
Use fit to create acceptance/functional tests below GUI
Expand coverage of automated GUI acceptance tests
Prasad, Salim