Haiku #9

'tis a blissful fate
captured by your mermaid smile
and drowned in your eyes

Leaders in Agile - TDD - Virtual conference

On Wednesday 2nd March I attended a virtual conference on Test Driven Development (TDD) hosted by bzmedia. Guest speakers were Kent Beck and Mark Seeman.

TDD is an Agile methodology where software is written in small increments by creating a test that fails then writing the code to make the software pass the test. Once passed, another test is created, the code implemented to pass the test and so on.

A test takes an input, defines an expected output and compares the actual output with the expected one

By breaking up the code into these small chunks (where each chunk should only take around 15mins), comprehensive unit tests are created, and design decisions are made, by the developer as the code is being produced.

The software is complete once you have run out of tests to implement.

In following this method it is possible to reduce the cost of fixing defects on the basis that the longer a defect exists, the longer it will take to find and fix.

unit tests

There are 2 types of tests: those that test the functionality/logic of the code and those that test the implementation. Implementation tests are owned by the software architect; the developer has ownership of the unit tests which test the logic in the code. It is the unit tests that form the basis of TDD and provide the framework required to develop working code.

Not all the functionality can or should be tested; focus on the most important logic

To effectively build unit tests the code needs to be abstract, i.e it needs to function as a separate unit to everything else. This way any external influence can be ruled out as a cause on the results of the test, if the code does have some dependencies then it should be possible to create test doubles which can be used to provide controlled input to the code being tested.

deferred design decisions

Throughout the development, design decisions are being made. The test will be given a name which can then be given to the object/function that is being tested, likewise the names of variables will come out of creating the test. In the end the test suite will define how to communicate with the code (the Interface)

Best practices should be strictly adhered to: objects/classes should be loosely coupled, refactor to avoid repeating yourself by creating helper objects/methods to facilitate code re-use. As the unit tests will already be in place for the existing functionality it will make it easier to validate the changes made during refactoring.

maintaining tests

One of the more challenging aspects of TDD is keeping the test suite up-to-date.

It is not unreasonable to expect twice as much test code as that in the actual software

Even though there will be a lot of test code it would not make sense to create tests for the test suite so the complexity of unit tests should be really simple.

Refactoring is an important part of maintenance so helper methods/classes/frameworks should be used to isolate complexity, this comes at a cost though of creating coupling. The dependency of the tests on the helper methods means that one of the biggest challenges is writing the interface for them as any change to it could break many tests. It is important to minimise the coupling and therefore the chances of creating these fragile tests as they tend to get abandoned or changed when they break.

The code is written to pass the test; the test is not written to pass the code

Summary

• Reduced defect costs


• Defer bugs to the test suite rather than the software


• Software designed during development, by developer


• Tests are written one at a time


• Tests should be written to fail, then software coded to pass


• Tests are automated


• Keep time tests take to run minimal


• Outsourcing development isnt Agile

Wednesday playlist

7:Moby
6/8 War:Leftfield
6 Underground:Sneaker Pimps
The 29/8 Steps:Outside
21st Century Poem:Leftfield
World Looking In:Morcheeba
Women Lose Weight:Morcheeba
Why does my heart feel so bad:Moby
What You Think About...:St. Germain
What New York Couples Fight About:Morcheeba
Western Eyes:Portishead
A Well Deserved Break:Morcheeba
Way Beyond:Morcheeba
Waterbaby:Sneaker Pimps
Wasted Early Sunday Morning:Sneaker Pimps
Walking Zero:Sneaker Pimps
Undress Me Now:Morcheeba
Undenied:Portishead
Tosh:Fluke
To Forgive But Not Forget (Lim' Chol V'lo Lishkoach):Outside
Tesko Suicide:Sneaker Pimps
Teardrop:Massive Attack
Swords:Leftfield
Sure Thing:St. Germain
Storm 3000:Leftfield
Stoppa - Drum Head:Stoppa
Spin Spin Sugar:Sneaker Pimps
Space Shanty:Leftfield
Space Junk:Burning Bush
South side:Moby
Song Of Life:Leftfield
So Flute:St. Germain
Slowdown:Morcheeba
Shallow End:Morcheeba
Seven Months:Portishead
Sao Paulo:Morcheeba
Salt Water Fish - Peshay Mix:Ruby
Rushing:Moby
Run On:Moby
Rose Rouge:St. Germain
Rome Wasn't Built In A Day:Morcheeba
Roll On:Sneaker Pimps
Risingson:Massive Attack
Rino's Prayer:Leftfield
Remembrance:Outside
Release The Pressure:Leftfield
Public Displays Of Affection:Morcheeba
Post-Modern Sleaze:Sneaker Pimps
Porcelain:Moby
Pont Des Arts:St. Germain
The Plan:Outside
Phat Planet:Leftfield
Peace - Pts 1 & 2:DJ Food
Over:Portishead
Otherwise:Morcheeba
Original:Leftfield
Open Up:Leftfield
Only You:Portishead
Only The Strong Survive:DJ Krush
One To One Religion:Bomb The Bass
Nights Introlude:Nightmares On Wax
Natural Blues:Moby
Mutant Jazz:T-Power Vs. M.K. Ultra
Mourning Air:Portishead
Moodswing:Outside
Montego Bay Spleen:St. Germain
Minty:Outside
Mezzanine:Massive Attack
Melt:Leftfield
Man Next Door:Massive Attack
Machete:Moby
The Lower We Fly:Outside
Low Place Like Home:Sneaker Pimps
Love Sweet Love:Morcheeba
Love Is Rare:Morcheeba
Let It Go:Morcheeba
Leave Home:The Chemical Brothers
Latin Note:St. Germain
Land Of...:St. Germain
La Goutte D'Or:St. Germain
Killing:Olive
Karmacoma - Unkle Situation Mix:Massive Attack
Journeyman, Pt. 2:Outside
Journeyman, Pt. 1:Outside
Journeyman Pt 2:Outside
Isobel:Björk
Inspection Check One:Leftfield
Inside:Moby
Inner City Life:Goldie Presents Metalheads
Inertia Creeps:Massive Attack
In The Hands Of The Gods:Morcheeba
If things were perfect:Moby
I'll Fly Away:Ballistic Brothers
Humming:Portishead
How Do:Sneaker Pimps
Honey:Moby
Half Day Closing:Portishead
Guitar Flute & String:Moby
Group Four:Massive Attack
The Great London Traffic Warden Massacre:Morcheeba
Good Girl Down:Morcheeba
Get Along Ft. Pace Won:Morcheeba
The Garden Of Earthly Delights:D Note
Friendly Pressure - Pluvio Mix:Jhelisa
Fragments Of Freedom:Morcheeba
Flowers Aren't IV Picking:Outside
Find my Baby:Moby
Fallen (Slight Return):Ape
Exchange:Massive Attack
Everloving:Moby
Elysium:Portishead
El Cid:Leftfield
Dusted:Leftfield
Dub Gussett:Leftfield
Down Slow:Moby
Double Flash:Leftfield
Dissolved Girl:Massive Attack
Cowboys:Portishead
Cool Kids Of Death - Underworld Mix:Saint Etienne
Commander Tom / Attention (Future Funk Remix):Various
Coming Down Gently:Morcheeba
Clubbed To Death (The First Mix By Rob Dougan):Rob D
Clank:DJ Spooky
Charango:Morcheeba
Chant Of A Poor Man:Leftfield
Bump:Dave Angel
Born Slippy:Underworld
Bodyrock:Moby
Black Milk:Massive Attack
Black Flute:Leftfield
The Big 'F' Reunion:Outside
Becoming X:Sneaker Pimps
Be Yourself:Morcheeba
Barbola Work:Black Dog, The
Aqualung:Morcheeba
Angel:Massive Attack
All Mine:Portishead
Afro-Left:Leftfield
Afrika Shox:Leftfield