Introduction to Extreme Programming. Extreme Programming is... Benefits. References: William Wake, Capital One Steve Metsker, Capital One Kent Beck

Transcription

1 Introduction to Extreme Programming References: William Wake, Capital One Steve Metsker, Capital One Kent Beck Extreme Programming is... Lightweight software development method used for small to medium-sized development projects Emphasizes: ongoing user involvement pay-as-you-go design incremental, test-first programming Benefits Quality software High maintainability Satisfied customer and development team 1

2 XP Principles Rapid feedback Assume simplicity Incremental change Embrace Change Quality Work XP Practices - Ongoing Small releases Establish metaphor Tests XP Practices - Environment On-site customer 40-hour week Open workspace 2

3 XP Practices - Development Planning game Pair programming Simple design Refactoring Collective ownership Continuous integration Coding standards Rights Manager and Customer: You have the right.. to an overall plan, to know what can be accomplished, when, and at what cost. etc. Developer: You have the right.. to know what is needed, via clear requirement stories, with clear declarations of priority. etc. XP Process Play the Planning Game Release Planning Iteration Planning Play the Programming Game 3

4 Planning Game Business people decide: scope priority dates of releases Technical people decide: estimates consequences process detailed scheduling Release Planning Large scale planning for the overall project Story is one thing that the customer wants the system to do Tasks: Create stories Prioritize stores Iteration Planning Developers determine what stories can be done within schedule Developer Tasks: Read customer stories Brainstorm tasks Estimate task completion time Negotiate with customer to accept tasks 4

5 Programming Game Incremental, test-first programming Tasks: listen build unit test Test everything that could possibly break code design (refactor) Tests Functional Tests Unit Tests Functional Tests Specified by the user(i.e. customer) Implemented by users, developers, and/or test team Automated Run at least daily Part of the specification 5

6 Unit Tests Written by developers Written before and after coding Support design, coding, refactoring, and quality. Code Approach Write a small test Run ==> compiler error Write enough code to compile Run ==> test fails Write enough code to pass the test Run ==> test succeeds Repeat from top Game Play Write code test-first Use JUnit for tests Track time for task completion 6

7 Design - part of coding Pay as you go Spike when necessary You aren t gonna need it Simplest thing that could possibly work Once And Only Once rule Refactoring Game Refactor code until it Works (passes tests) Communicates what it needs to Has no duplication Has as few methods and classes as possible Eliminate code smells Some Code smells Useless comments Almost (but not quite) duplicated code Classes too large Methods too long Too much dependence on primitives think class struct classes (getters & setters but little functionality) 7

8 Refactoring Example Extract Method : String s=reader.readline(); //assemble dashed string int p1 = s.indexof( # ); int p2 = s.lastindexof( # ); result = s.substring(0,p1) s.substring(p2, s.length()); : : String s=reader.readline(); result=assembledashedstring(s); : public static String assembleddashedstring(string s){ int p1 = s.indexof( # ); int p2 = s.lastindexof( # ); String dashed = s.substring(0,p1) s.substring(p2, s.length() ); return dashed; } Extract Method - Mechanics Create new method, named for what it does Copy code to new method (leaving old code in place) Adjust variables, parameters, return value Compile new method Replace original code with call to new Compile and test CLASS EXERCISE 8

9 Draw a Coffee Pot Planning Phase 2 customers write stories that describe major functionality of coffee pot 4 developers estimate time to completion(drawing the coffee pot) 2 moderators observe process and enforce rules of process Rules Every story has to have a time to completion All functionality desired by client must be found in one of the stories Always ask for help. If not involved in helping someone, then you must help if asked Draw a Coffee Pot Iteration Phase If not enough time or too much to do, ask client to pick smallest subset of functions that are acceptable Deliver the drawing with the simplest set of features that are acceptable and which can be done within estimated time 9

10 Resources Extreme Programming Explained, Kent Beck Refactoring,, Martin Fowler Further Information What Will We Use in Class Planning game Tests Pair programming Refactoring On-site customer Simple design Open workspace 10