A Taste of TDD: The basics of TDD, why it is hard and how to do it better

TESTING AND TDD
John McCaffrey
@ J_McCaffrey
Wednesday, October 29, 14

AGENDA
• Poll: What are your current testing practices?
•What is TDD?
•Where does it fit in the Agile landscape
• TDD basics
• Pros/Cons/Controversy
• Demo/Q&A

ME
• Started Unit testing in Java
• TDD Javascript & Ruby
• Love Testing and TDD

YOU
•What are you doing already?
•What are you hoping to learn?

TDD DEFINED

TDD DEFINED
• Software Development practice
• Focus on explicit expectations from tests
• Characterized by red/green/refactor

RED/GREEN/REFACTOR

TDD BENEFITS
• Correct behavior
• Rapid feedback
• Simpler, easier to understand
• Fully covered by tests
• Living documentation
• Confidence

TDD == GTD?
• Collect
• Process
• Organize
• Review
• Do it

• not just testing in general
• more of a design practice
with test benefits
• TDD is not a silver-bullet!

WHAT WE WILL COVER
•Where Testing and TDD fit in Agile
• General Agile Testing practices
• TDD Practice
• Pros/Cons/Controversy
• Demo/Q&A

TDD RESOURCES
• Blogs, Books, Workshops
• Confreaks.com
• pluralsight.com

WHY IS TESTING SO CRITICAL?

DOES OUR CODE...
• function correctly?
• handle expected edge cases and exceptions?
• allow for new features and change?
• make sense to new team members?

MO’ PROBLEMS
• Code changes create new bugs
• Fear of changing anything leads to worse code
• Estimates are higher, changes take longer
• Bugs, Bugs, Bugs, regression, Bugs, Bugs
• Time between build to feedback is too long

WITH TESTS
• Code change is safer
• Component design is clearer
• Feedback is quicker
• Safety and freedom to make the code better

TESTS ARE FOR EVERYONE
• Managers and Business team
• QA Team
• Support
• dev ops
• Customers

TESTING TYPES
• Unit
• Functional
• Integration/system testing
• User acceptance
• Manual testing

DIFFERENT TYPES OF TESTS

TDD APPLIED
• You can use TDD and Test-First with all types of testing
• TDD helps you focus on your specific task
• TDD may be challenging for some types of testing

TESTING & TDD
IN THE
AGILE LANDSCAPE

FEEDBACK IS KEY

AGILE:
FEEDBACK AT EVERY LEVEL

SHORTEST CYCLE

XP PRACTICES
• Planning Game
• On-site Customer
• Small Releases
• Simple design
• Customer Testing
• Metaphor
• Sustainable pace (40hr)
• Common Standards
• Collective Ownership
• Unit Testing
• Refactoring
• Continuous Integration
• Pair Programming

TDD FEEDBACK CYCLE
• Code is correct
• Design is workable
• Intention is clear
• Dependencies and collaborators are minimal
• It does what the Developer intended....

IF YOU ONLY GET ONE THING
OUT OF THIS...

IF YOU ONLY GET ONE THING OUT
OF THIS...
• Define acceptance test criteria as team, as part of the story
definition
• write out the test steps
• plan to automate them
• update with any test cases that are discovered

TDD WON’T FIX BAD
REQUIREMENTS!!

THE PAYOFF

THE AWESOME
• high coverage
• fast
• informative
• not brittle
• visible to the team

TDD IN PRACTICE

TERMINOLOGY
• Unit tests
• Setup/Fixture
• Assertion
• Coverage
• Design
• Interface/contract
• Mock/Stub
• DRY
• YAGNI
• Automated tests
• Continuous integration
• Continuous deployment

TDD WORKFLOW
• write the test, watch it fail
• write “just enough” code to make it pass
• rinse/repeat, improving the tests and code as you go

SIMPLE DESIGN
• Passes all the tests
• Minimal Duplication
• Maximizes clarity
• Fewest number of classes or methods

SIMPLE DESIGN
• Low Coupling
• High Cohesion
• High Encapsulation
• SOLID

TDD WORKFLOW
• New code
• Legacy
• Bugs

NEW CODE

STORY SAMPLE
• As a Standard User I need to see my list of
outstanding orders, so I can review and
complete them in priority order

STORY SAMPLE
• As a Customer I need to calculate the tip for
my bill, so I can save time and include a
reasonable amount

TEST CODE

TEST

CODE

LEGACY
• first, do no harm
• get sufficient coverage in place
• confirm existing functionality is correct
• review tests cases with team

TEST FIRST,
REFACTOR LATER
I’M SERIOUS!!

CODE SAMPLE

BUGS
• write a test to confirm the bug
• change the code to fix the bug
• the test should confirm the fix

PROS/CONS

PROS
• Focus
• Confidence
• Rapid Feedback
• Clear intention
• Executable documentation

CONS
• TDD is HARD!!
• Refactoring is an uncertain art
• Some parts are hard to test first
• False sense of security
• Focus more on the tests than the system!

ANTI-PATT3RNS
• huge setup, reused unnecessarily
• too much going on in one test
• only testing happy-path, not exceptions
• too much boiler-plate, basic tests
• over-mocking: “tests pass, but production is broken”
• not doing the ‘refactor’ part of Red/Green/Refactor

CONTROVERSY

CONTROVERSY
• Used to love and promote TDD
• Dogmatic TDD is not helpful
• Focusing exclusively on speed and low-coupling
• Shaming others for not following “TDD or Die!”

SUMMARY
• Tests are worth the investment
• Everyone on the team should care about them
• TDD is a great way to improve your code and tests
• Find an approach that works best for your team

RESOURCES
• TDD is Dead - David Heinemeier-Hansson
• R.I.P. TDD - Kent Beck
• TDD “straw-men and rhetoric” - Gary Bernhardt
• Failures of “Intro to TDD” - Justin Searls
• Pragmatics of TDD - ‘Uncle’ Bob Martin
• When to Mock - ‘Uncle’ Bob Martin
• TDD Failed to become mainstream
• TDD a Love-Story - Nell Shamrell

LET’S HAVE SOME
QUESTIONS!
John McCaffrey
@ J_McCaffrey

A Taste of TDD: The basics of TDD, why it is hard and how to do it better

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