a little software engineering: agile software development, practices through values

A little Software Engineering:

Agile Software Development,Practices through Values

C Sc 335Rick Mercer

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Goal and Outline

Main Goal:– Suggest practices, values, and some process for

completing a final project on time that is better than any one person could do it in in four times the time

Outline– Distinguish Waterfall (plan driven) from Agile– Practices and Values of quality software

development

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Waterfall Model

Waterfall was described by 1970Understood as– finish each phase– don’t proceed till done

W. W. Roycecriticized this– proposed an iterative approach

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Became Popular

Management (usually software ignorant) like phases – to easily set deadlines

Customers provide all requirements Analysts translate requirements into specificationCoders implement the specification Reviews ensure the specification is met Testing is performed by testers (not the devs) (QA)Maintenance means modifying as little as possible – old code is good code

Change is hard (and costly)

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To waterfall or not

Waterfall became popular, and for no good reasons– This process is still is used a lot

Craig Larman's book [1] provides proof that waterfall is a terrible way to develop software – In his study, 87% of all projects failed – The waterfall process was the "single largest contributing

factor for failure, being cited in 81% of the projects as the number one problem."

[1] Agile and Iterative Development: a Manager's Guide, Addison-Wesley Professional, 2003

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A Spiral Approach

Dr. Barry Boehm proposed a spiral approach

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Agile Software Development

set of practices to produce high-quality softwaredisciplined approach to software developmentsuccessful because it emphasizes customer involvement and promotes team worknot a solution looking for a problem59% of 2013 survey respondents use Agile– 83% planned to use agile in the upcoming year

The Agile Manifesto:a statement of values

Process and toolsProcess and toolsIndividuals and interactionsIndividuals and interactions

over

Following a planFollowing a planResponding to changeResponding to change

over

Source: www.agilemanifesto.org

Comprehensive documentationComprehensive documentationWorking softwareWorking software over

Contract negotiationContract negotiation

Customer collaborationCustomer collaboration

over

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eXtreme Programming (XP)an Agile Process

Values– Communication, Simplicity, Feedback, Courage

Principles– Provide feedback, assume simplicity, make incremental

changes, embrace change, quality workPractices– Planning game, small releases, simple designs, automated

testing, continuous integration, refactoring, pair programming, collective ownership, continuous integration, on-site customer, coding standard

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Cost of change

Costof

change

time

Waterfall

Agile

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Cost of the Project

Paraphrasing from two companies I've talked to (probably many more)

When we bid projects, we charge $X for doing it Waterfall and $X/2 for doing it Agile

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Agile Practices: The Planning Game

The planning game involves user stories– Short descriptions of desired features– Provide value to customer– Testable (do we have that feature two weeks in?)

Clients write stories and prioritize them– In 335, SLs wrote the requirements, you prioritize

Developers estimate how long a story takes– If you are so inclined, estimate each requirement

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Values: Communication

Simply talking about the projectDetermining who will do whatUnderstand Requirements– Write user stories to represent what the system will do

Analysis & Design sessions– Happening whenever the team is together

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Values: Communication

Pair programming – A good thing

Iteration planning– What to do in the next iteration

Retrospectives, for example what do we– Stop doing– Continue doing– Start doing

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Values: Feedback

Feedback very important

– Small Iterations– Pair programming– Constant code review (pair programming)– Continuous integration (add often to the build—sync

your code with the system)• Check out, run all test including your new tests and code,

if all pass, check in the updated system– Automated unit tests (JUnit)

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Values: Feedback

Compiler feedback: secondsPair programming feedback: half minutes– Complete all tasks completed in a pair programming mode.

Unit test feedback: few minutesAcceptance testing: Each Iteration– Your PM has accepted Iteration 1 or told you what’s missing

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Practices: On-site customer

Many software projects fail because they do not deliver software that meets needsA real client should be part of the team– Defines / decides the needs– Answers questions and resolves issues– Prioritizes features– Helps prevents devs from making decisions like:

"They probably wanted us to ....”Consider your PM playing this role

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Practices: Simple design

The “right” design– Runs all tests– No code duplication, No code duplication, No code

duplication– Composed methods

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Practices: Testing

Software should be tested, but it is often spotty or overlookedAutomatic testing (JUnit, for example) helps us know that a feature works and it will work after refactoring, additional code, and other changesProvides confidence in the program

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Testing

Write tests at the same time as production code– Unit tests developer– Feature/acceptance tests grader in 335

Don't need a test for every method (but why not?)Testing can be used to drive development and design of code– But it helps to have an overall architecture first (see your UML

class diagram, which is subject to changeAllows for regression testing– Did my change break previously working code?

• If well-tested, you see the red bar when you break your code

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Regression Testing

Regression Testing – re-testing of a previously tested program following

modification to ensure that faults have not been introduced or uncovered as a result of changes.

– Regression tests are designed for repeatability, and are often used when testing a second or later version of the system under test

– Regression testing can be carried out on all applications, including e-Commerce and web-based systems

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Testing

Strong emphasis on regression testing– Unit tests need to execute all the time

Unit tests pass 100%Other testing frameworks include– SUnit (Smalltalk), HttpUnit (WebApps), AceUnit (C), CPPUnit

(C++), PyUnit (Python)– For a complete list, seehttp://en.wikipedia.org/wiki/List_of_unit_testing_frameworks

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Can't unit test always

Won’t have unit tests for– GUIs: There are testing frameworks to simulate and test

user interaction, but not this course• Just added to WebCat

– Network, use visual inspection while running– Views, animation, drawing: visually inspect

• this is system verification too– Randomness: Some strategies might have some

randomness, which can be hard to work with• Use “tournaments” to see which AI wins, print restults

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Practices: Refactoring

Restructure code without changing the functionalityGoal: Keep design simple– Change bad design when you find it– Remove “dead” code

Examples at Martin Fowler's Web site: http://www.refactoring.com/ see online catalog

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Practices: Pair programmingWrite production code with 2 people on one machine– Person 1: Implements the method (Driver)– Person 2: Thinks strategically about potential improvements, test cases,

issues (Observer or Navigator)Pairs change all the time. Has advantages such as– No single expert on any part of the system– Continuous code reviews, fewer defects– Cheaper in the long run, and more fun

Issues with Pair Programming:– Not all people like it, not everyone gets along– Pairs need to be able to work together (tough in college)– Requires tolerance, acceptance, showers, no bad breath

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Practices: Collective ownership

All code can be changed by anybody on the teamEverybody is required to improve any portion of bad code s/he seesEveryone has responsibility for the systemIndividual code ownership tends to create "experts", the "experts" tend to create difficult team situations– Every year in 335...

What would you do? – A team member does not like curly brace line up the other 3

do. Should we go with 1, 3, or negotiate?

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Practices: Continuous integration

Integration happens after a few hours of developmentCheckout repo with your changes,

– which may require handling conflicts of two people have modified the same class or method

Make sure all tests pass (green bar)In case of errors:

– Do not put changes into the repo, fix them firstCheck in the system to the common repositoryRepeatYour team should be using Git from command line

– Recommended: do not use the Egit plugin

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Continuous Integration

Find problems earlyCan see if a change breaks the system more quickly -- while you remember the detailsAdd to the build on BitBucket in small increments– Every few hours, or – after any new feature, or– When it feels right

• Nice to have all 4 in the same room so everyone knows

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Practices: Coding standards

Coding Standard– Naming conventions and style– Least amount of work possible: Code should exist once

and only once– Everyone always use Java 7 always

Team has to adopt a coding standard– Makes it easier to understand other people’s code– Avoids code changes due to syntactic preferences– You get to fight over curly brace placement

Coding Standard with Eclipse

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You may use the Eclipse Standard