Scrum and Test-driven development

Software Development Methodologies: Scrum and Test-Driven Development Gábor Török, Agil Eight Oct 15, 2007 Forum Nokia Developer Day, October 2007

Agile Software Development

“ Agile methods are a family of development processes, not a single approach to software development. ” ( Wikipedia )

Some basic principles

Frequent delivery == short iterations

Close (preferably face-to-face) cooperation with business people and developers

Simplicity

Self-organizing teams

Regular adaptation to changing circumstances

Trusted people , fewer but more competent

Cost-effective , an answer to the changing needs of recent years: producing quality software in shorter time, react on rapidly changing requirements more efficiently.

Developer Day, October 14 th – 15 th 2007

Agile Software Development

Whilst being incremental agile development differs from other methods in that its time periods are measured in weeks rather than months and work is performed in a highly collaborative manner.

Compared to the Waterfall model

The waterfall model is the most predictive of the methodologies, stepping through requirements capture, analysis, design, coding, and testing in a strict, pre-planned sequence.

Waterfall model is inflexible : commitments are made early on, and it is difficult to react to changes in requirements.

Agile methods, in contrast, produce completely developed and tested features (a very small subset of the whole, though)

Scrum

“ Scrum is an iterative, incremental process for developing any product or managing any work.” ( www.controlchaos.com )

Its attributes are

Wrapper for existing engineering practices

Produces a potentially shippable set of functionality at the end of every iteration

Short iterations, typically between 2-4 weeks

Cross-functional team, close co-operation with customer

Prefers rapidly changing requirements

Scrum

Characteristics of Scrum

Product backlog: prioritized list of tasks to be done

Sprint: iteration of work, typically between 2-4 weeks

Sprint planning session/review: meeting for planning the upcoming sprint or reviewing what the team has achieved

Daily scrum: short daily meeting for team to synchronize

Roles

Product Owner: representative of customer/stakeholders

ScrumMaster: facilitator for the team and product owner

Team: people doing the actual work

Burndown chart: shows remaining work over time. X axis is time, Y axis is work.

Scrum Developer Day, October 14 th – 15 th 2007 ( www.controlchaos.com )

A software development technique that involves repeatedly first writing a test case and then implementing only the code necessary to pass the test.

As an aspect of Extreme Programming (XP), TDD requires that an automated unit test is written before each aspect of the code itself.

Development cycle

Add a test

Run all tests and see the new one fail

Write code that satisfies test

Run all tests again and see them succeed

Refactor if neccessary

Test-Driven Development (TDD) Developer Day, October 14 th – 15 th 2007

Benefits

Less use of a debugger

Less defects

Build software better and faster  it drives design and looks functionality from user's point of view

Limitations

Code quality is much based on the quality of the test itself  discussions and code reviews are needed to avoid low-quality code

TDD is difficult to use in some situations, such as graphical user interface or relational database  mock objects can help

Mock objects are simulating objects that mimic the behavior of real objects in controlled ways. The aim is that production code should be unaware of whether it's using mock or real objects.

Tools (Symbian)

SymbianOSUnit from Penrillian

Based on open source CxxUnit  developers may be familiar with it

Unit++

Also open source: http://unitpp.sourceforge.net/

EUnit from SysopenDigia (commercial)

etc.

No mock object framework for Symbian , there are some for C++ in general (e.g. Mockpp)

Continuous Integration (CI)

“ A software development practice where members of a team integrate their work frequently , usually each person integrates at least daily.” (Martin Fowler)

CI leads to significantly reduced integration problems and allows a team to develop cohesive software more rapidly  reduced risks .

On completing the definition

Automated, self-testing and fast builds

Make it easy for anyone to get the latest executable

Automate deployment

Everyone can see what's happening: progress, statistics on code coverage/tests, etc.

Continuous Integration (CI)

Tools (Symbian)

First of all, there are no CI tools around specific for Symbian development

CruiseControl

Java (Ant, JUnit), .NET (NAnt, NUnit) or Ruby-based versions

Open Source

Anthill

Java- and Ant-based

Open Source

Continuum

Java- and Ant/Maven-based

Open Source

A Working Solution Developer Day, October 14 th – 15 th 2007 CruiseControl Build tool Build script Ant SDK with build tools SVN checkout clean build test package builds reports notification / monitoring commits changes SymbianAnt SymbianOSUnit Symbian performs uses uses uses gets data from executes artifacts

A Working Solution