Testing distributed, complex web applications

Testing of distributed
applications
Rails Way Con 2011
Jens-Christian Fischer
with Michael Mahlberg & Keith Bingman

jcf@mobino.com

@jcfischer

Freitag, 3. Juni 2011

le x
m p
co
Testing of distributed
applications
Rails Way Con 2011
Jens-Christian Fischer
with Michael Mahlberg & Keith Bingman

jcf@mobino.com

@jcfischer


Agenda

• Background
• What & Why & How of Testing
• Discover the state of your apps
• Make testable apps

we move money


What is behind?
1 Rails app
5 Sinatra apps
1 Ruby daemon
1 VOIP Server
1 Speech Synthesizer
1 SQL Database (Postgres)
1 NoSQL Server (Redis) (with Resque)

Architecture


Merchant Web
Customer Web Customer Voice
Widget

Volcker Trichet Freeswitch

Duisenberg Keynes Greenspan

Redis Smith VAAS

Postgres 9 Acapela


Merchant Web
Customer Web Customer Voice
Widget

Volcker FrontTrichet Freeswitch

Duisenberg Keynes Greenspan

Back Voice
Redis Smith VAAS

Database
Postgres 9 Acapela


Trichet Volcker Duisenberg

Greenspan Keynes Smith

Testing


The old days

• Simple web apps
• Click through testing


Testi
g n
Royce, W. (1970). Managing the development of large
software systems. Proceedings of IEEE Wescon.

In Rails
—
everything is better


Automated Tests

Unit
Integration
Frontend tests

Complexity
• Modern applications consist of
many pieces
• App Servers, DB, NoSQL, Speech
WebServices, Telephony,
Synthesizers
• HTTP, Line Protocols, JSON,
XML, Corba, RMI


What to test
Robert „UncleBob“ Martin:
•Unit Tests
•Component Tests
•Integration Tests
•System Test
•Manual Tests
http://stackoverflow.com/questions/2965483

Unit Tests

• Close to 100% code coverage
• Test Driven Development
• Written by Programmers


Component Tests

• Test ~50% of the System
• Cucumber / Selenium / Fitnesse
• Written by QA & Analysts
• Happy Path & some unhappy
paths


Integration Tests

• Cover ~20% of system
• Test assembly of components
• Written by Architects

System Tests

• Cover 10% of the system
• Test the whole system
• Written by Architects

Manual Tests
• Exploratory Manual Tests
• Manual but not scripted
• Human ingenuity & creativity
Bach, J. (n.d.). Exploratory testing explained. Online:
http://www. satisfice. com/articles/et-article. pdf.


Where do we
test?

Testing the
edges

How do we
test?

http://blog.objectmentor.com/articles/2009/09/29/
ruining-your-test-automation-strategy

Tools of the trade
Selenium
Cucumber
Steak
capybara
webkit
zombie

only cover a minimal
part

the web frontend,
but our apps are so much
more


Decoupling

Systems diverge
APIs diverge


Web Services

Many services
outside our control


Synchronizing

• Tests require complex state
across several systems
• Tests involvebetween systems
interactions
complex


Questions


Questions to ask

• Development
• Testing
• Production


Development

Is the system I‘m
building correct?


Test

Do all the pieces of
the system work
together?


Production

Are all parts of my
system working?


Development
• Test Driven Development only
takes you so far
• Test a single component
• Unit tests in work, but don‘t
components
multiple

„cross the chasm“


Development
• Setting up a complete system for
development can be taxing
• pow to the rescue
http://pow.cx/
• Foreman
https://github.com/ddollar/foreman


Testing

• Integration tests need to
stress complete application
stack
• Does your CI Server handle
this?


Outside your
app

Write Mock Services

• If youitdon‘t control it,
mock
• „Rails Enterprise ready ™ “


Mock Services
• Allowsspecification against a
„real“
you to code

• Allows of said code against
failure
you to
service
• Gives you a stick to beat up
the developers of said service
(„Rails-Enterprise ready“ ™ )


Making it
work

Version Control
Repository setup
One Big repository?
One repository for each
component?
Tagging / Syncing


Development Servers
Webrick doesn‘t scale

but:
it‘s „easy“ for Rack based apps
pow by 37 Signals
(Mac Only)


Configuration

Configuring half a dozen applications
Again: Synchronisation
Inject configuration (Example Picky)
http://florianhanke.com/picky/


Production

Is my system working correctly?
Probes
• DTrace (OSX, Solaris)
• Monitoring (Scout, NewRelic)
• Your own probes


Car industry

If car manufacturers would build
engines the way enterprise IT
systems are built, you‘d need to
remove the engine from the car
and disassemble it completely to
find a fault
— @MMahlberg, 2011

OBD
• 1996: The OBD-II specification is made mandatory for
all cars sold in the United States.
• 2001: The European Union makes EOBD mandatory for
all gasoline (petrol) vehicles sold in the European Union,
starting in MY2001 (see European emission standards
Directive 98/69/EC [1]).
• 2008: All cars sold in the United States are required to
use the ISO 15765-4 [2] signaling standard (a variant of
the Controller Area Network (CAN) bus).

http://en.wikipedia.org/wiki/On-board_diagnostics


Solved Problem


http://the-adam.com/adam/rantrave/ibm_360.jpg

Diagnosis Channel

• Known from Car / Planes / Mainframes
• Red lights on your dashboard
• Complete diagnosis of system possible
• Complete remote control possible

Rolls Royce

• InFlight Diagnosis of engines
remotely


Dashboard

• Look into state of application
• Sanity Checker


Dashboarding

• Extract relevant data from
your system
• How many req / s
• How many logins
• Delta / Trends

SanityChecker

• API stateallows you to extract
the
that
of your app
• DB there?
• All neighbouring components
reachable?


Chaos Monkey

• Random failures
• Better reliability


Build testable apps
• Expose your internals (through APIs)
• Use SOLID design
• Single Responsibility Principle
• Open Closed
• Liskov Substitution Principle
• Inversion of Control
• Dependency Injection

Testable apps

• Obey the abstraction layers
• keep of abstractionat it‘s own
level
each method


Build probe-able apps

• Measure APIs
$
rails
console
production


Build controllable apps
• Call functionality of the app
• Create new user
• Create transactions
• Delete stuff
• Do stuff
• ...

Test user / Magic
• In „Enterprise“ systems:
• Test Company
• Test User
• Test Accounts
• Are those in production system?
• Do everything - or not quite?

Use production data
in development / test


Wrapping up


What & Why & How of Testing
Discover the state of your apps
Make testable apps


Thank you!


Credits

• http://www.flickr.com/photos/
myoldpostcards/4020087797/
• http://www.flickr.com/photos/
benncapon/390585495/
• iStockphoto

License

http://creativecommons.org/licenses/by-nc-sa/2.5/ch/

Testing distributed, complex web applications

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