a beginners guide to test driven development
TRANSCRIPT
A Beginners Guide to
Test Driven Development
Developing Sustainable Software….
Naresha K.,
Software Craftsman
Twitter: @naresha_k
Disclaimer
The opinions or views expressed
in this presentation are solely of
the speaker and do not necessarily
represent the views of my
employer.
You are Here
http://www.flickr.com/photos/oldben/2322196242/
The Roadmap
You are here Threat Driven Development
Destination Test Driven Development
The Significance
Never
in the field of software development
have so many owed
so much to
so few lines of code
The Problems
http://www.flickr.com/photos/donnagrayson/195244498/
Cost of Change
2
20
50
100150
500
Analysis Design Coding Integration Acceptance Production
Cost
Cost
Time To Market
http://www.flickr.com/photos/cobalt/5800169708/
Sustainable Software
http://www.flickr.com/photos/sillygwailo/146872543/
We are only afraid of…
http://www.flickr.com/photos/spursfan_ace/2328879637/http://www.flickr.com/photos/crystaljingsr/3914729343/
We are only afraid of…
http://www.flickr.com/photos/spursfan_ace/2328879637/
Planning – The Waterfall way
http://www.flickr.com/photos/vizzzual-dot-com/2655969483/
The waterfall way
Analysis
• 2 weeks
Design
• 3 weeks
Code
• 4 weeks
Test
• 4 weeks
Release
• 14th
week
The fall of waterfall
Analysis
• 2 weeks
• 2 weeks
Design
• 3 weeks
• 4 weeks
Code
• 4 weeks
• 5 weeks
Test
• 4 weeks
• 2 weeks
Release
• 14th
week
• 14th
week
Testing can only indicate the quality
http://www.flickr.com/photos/24560044@N08/5726488676/
But Feedback is Important
When to receive feedback?
• Closest to the incident
• Frequently
• You get more time to act upon
Test Early Approach
• Test as and when you complete small chunk of
code (say a function – is it small?)
• Integrate
– Early, Small & Often
– But involves cost
Nature of Business Environment
http://www.flickr.com/photos/oldben/2301828397/
Mistaken Assumption
http://www.flickr.com/photos/9465588@N05/3302103347/
The Solution
Embrace Change
Automated Testing
• Mitigates
– Integration testing cost
– Regression testing cost
Benefits
• S - Savings through early integration
• C - Cost of automating tests
• ROI = S / C
• (Small + Often) integration => more S
Still Problems !!
http://www.flickr.com/photos/mosmancouncil/3361174929/
Waste
• Unused Code
• Lack of modularity
The Ultimate Solution
• Write test code before production code
How Writing Tests Help?
• Clarifies the acceptance criteria
• Encourages to write loosely coupled components
• Adds executable description of what code does
• Regression suite
How Running Tests Help?
• Detects errors (early)
• Lets us know when we have done enough
• Avoid unnecessary features
Test Driven Cycle
1. Write failing Tests
2. Write code pass tests
3. Refactor
TDD – Rule #1
No code will be written
without a failing test
TDD – Rule #2
No more tests will be written
Than sufficient to fail
TDD – Rule #3
No more code will be written
than sufficient to pass
failing tests
Demo
Feedback from tests
Unit tests End-End testing
Am
ount
of
Fee
dbac
k
Internal Quality Feedback
External Quality Feedback
White Box Black Box
http://www.flickr.com/photos/winning-information/2325865367/
http://www.flickr.com/photos/winning-information/2325865367/