Continuous Integration
Todd
Papaioannou

Or,
how to build software
better, faster, cheaper

What??

What is CI?
a development methodology
of daily developer integrations
verified by automated builds

What is it not?
nightly builds
developer branches
scheduled Integration Points
building via IDEs

Continuous
Compilation
!=
Continuous
Integration

‘Fraid Not!

Why do it?

Building software can
be a risky business

Risk 1:
Fixing bugs late is costly
Source: http://www.agitar.com/solutions/ why_unit_testing.html

So why is most
software built Requirements
this way?
Design
Implementation
Testing

Risk 2:
Lack of team cohesion
“Your changes to Bar are incompatible with
mine. How do we merge now?”
“When did we decided to upgrade to version
2.0-alpha of the Super library??”
“I thought you fixed that 2 months ago!”

Risk 3:
Poor quality code base
“We have 3 classes doing the same thing??”
“Everybody knows double checked locking is
a Bad Idea!”
“Why can’t I just include Foo and not require
all of the other 13 libs?”

Risk 4:
Lack of project visibility
“What do you mean the tests are failing?”
“What’s in version 1.2.3 of the build?”
“What’s our code coverage now?

Risk 5:
Lack of deployable software
“It works on my machine!”
“I need a new build to test with”
“The [boss|customer|patron] is coming,
we need to demo progress asap”

Use Continuous
Integration to reduce
the risks

Wait!
Didn’t you say
better, faster,
cheaper?

Better
Build better quality software
That is tested early and often
That adheres to best practices
and coding standards

Faster
Test in parallel, not at the end
No integration points
Builds become a non event

Cheaper
Identify defects earlier
Fix when least costly
Easily repeatable testing

So what
constitutes
a build?

Compilation
!=
A Build

Build Ingredients
Compilation
Test execution
Database integration
Code inspection
Automated deployment
Documentation generation

Compilation
Ensures code actually compiles
On every target platform

Test Execution
Ensures product functions
as expected
Through repeatable testing

DB Integration
Ensures DB and code in sync
Automates (re)creation of
DB and test data

Code Inspections
Ensures a healthy code base
Identifies problems early
Enforces best practices

Automated
Deployment
Products can be released anytime
Continually demo-able state
Eliminates “works on my machine”

Documentation
Generation
Ensures documentation is current
Removes burden from developers
Produces build reports and metrics

How do I
get started?

When do I build?
At every check-in
Every time a dependency changes

Dependency
Graphs Matter!

How do I build?
Use a single build script
That can run from the cmdline
Do not depend on an IDE

Do it continuously
Use a dedicated CI server, not cron
Trigger on all daily check-ins
Not [only] at midnight

Pay attention
to your builds
Provide immediate feedback
Make it easily accessible
Require no developer effort

Metrics Matter
Identify key metrics and
track them visually
Act on them immediately

The 7 step
program

Learn it,
Use it!

Step 1
Commit Early,
Commit Often

Step 2
Never commit
broken code

Step 3
Fix build failures
immediately

Step 4
Fail Fast

Step 5
Act on metrics

Step 6
Build in every
target environment

Step 7
Create artifacts
from every build

print
me!
1. Commit Early, Commit Often
2. Never Commit Broken Code
3. Fix build failures immediately
4. Fail Fast
5. Act on metrics
6. Build in every target environment
7. Create artifacts from every build

Summary

Continuous
Integration
can help you build better
quality software faster,
with more confidence

Start using it!

The End

Roll the Photo Credits
http://www.flickr.com/photos/24263322@N05/2403969648/
http://www.flickr.com/photos/destinme/1267500829/
http://www.flickr.com/photos/legacyalive/891467616/
http://www.flickr.com/photos/tizianoj/1294103746/
http://www.flickr.com/photos/xeophin/2181342710/
http://www.flickr.com/photos/booddin/2190614236
http://www.flickr.com/photos/thomashawk/176219254
http://www.flickr.com/photos/7446536@N03/430561725
http://www.flickr.com/photos/gallerisager/471366272
http://www.flickr.com/photos/mccain007/2092664145