Beyond Unit Testing: The Real Value of Test-Driven Development - Slalom

Beyond Unit Testing
Anthony Sciamanna
@asciamanna
anthonysciamanna.com
The Real Value of Test-Driven Development
October 11, 2019

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TDD Refresher
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Let’s go back in time!
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Discovered at Hunter Industries in 2011 by a team
coached by Woody Zuill
1994
A Very Brief History of TDD
Kent Beck releases the first version of the
SUnit framework for Smalltalk
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1994
1995
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Kent demos TDD to Ward Cunningham at
OOPSLA Austin in October. Details of the C3
Project start being publicized

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1994
1995
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Kent releases Extreme Programming
Explained
1999
Kent demos TDD to Ward Cunningham at
OOPSLA Austin in October. Details of the C3
Project start being publicized

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TDD Is a Testing Practice
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I don’t care if people write tests first or last.
As long as they get written.
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“
”
- Anonymous Tech Lead

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Ignores Design and Workflow Benefits of TDD

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Benefits of TDD

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Benefits of TDD
Test Suite
Externally Visible Artifacts

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Benefits of TDD
Test Suite
Software
Design

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Benefits of TDD
Test Suite
Software
Design
Developer
Workflow

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TDD Triple
Balance
Made
Making
Maker

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Benefits of TDD
Test Suite
Software
Design
Developer
Workflow

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Test Suite Benefits
Why we prefer TDD-style tests over Test After Tests

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Test Suite
Quality
Production
Code
Quality
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Disclaimer #1
Test suite quality influences production
code quality and vice-versa

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You Can’t Write Good Tests for Bad Code
• Wrapping non-testable code in unit tests
results in brittle, low-quality tests
• Test-first practices enable writing high
quality production code and high-quality
tests
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The TDD Quality Cycle
Test Suite Production Code
2. Code under test must be
testable (loosely coupled)
Refactoring
Refactoring
3. Enables tests to be
small, precise, fast,
isolated and independent
Virtuous
Cycle
1. Tests are written first

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Microtest
A short, simple, fast, isolated*,
test that probes the behavior
of a single class
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*Isolated does not mean we have to mock every dependency

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Microtests Don’t
Access a network
Access a database
Access the filesystem
Depend on other tests
Require a complex environment to run in
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S
O
S
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Small
O
S
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Small
Obvious
S
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Small
Obvious
Simple
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Small
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~12 LOC or less per test

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Obvious

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Arrange
Act
Assert
Arrange – Act – Assert
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Or
Given - When - Then

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Standardize common test constructs
Create the object under test in Setup
Standard name result to be asserted
Standard name for object under test
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Simple
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Avoid branching
and flow control
logic in tests

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How To Stop Hating Your Test Suite
Logic in tests confuses the story of what’s being tested. Test-
scoped logic is hard to read and errors are easy to miss.
- Justin Searls, Co-founder Test Double
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How To Stop Hating Your Test Suite
Test code is untested code!
- Justin Searls, Co-founder Test Double
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Test After Test First
Manual testing often takes
precedence
Unit testing at end tends to be
skipped to hit deadlines
All code is tested as it is created or
modified
Feels like busy work if code is manually
tested and considered “done”
The test is the path to changing the
system
Code is not influenced by tests to be
testable
Code is influenced by the tests to be
testable
Tests don’t serve as feedback loops Tests are continuous feedback loops,
supports refactoring and software design
Tests don’t get refactored – created at
end
Tests are continuously refactored
Tests are less comprehensive when
added at end
Tests are more comprehensive when
added with each code change
Coverage as a build gate often required
(commonly 70% coverage)
Coverage metrics unnecessary

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Software Design Benefits
Tests guiding quality software design

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Disclaimer #2
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TDD influences design quality
But it’s not a silver bullet

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Disclaimer #2
TDD alone influences
design quality
High Cohesion Loose Coupling
Small Classes Small Methods

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Disclaimer #2
TDD provides a mechanism
for learning software design
Small Classes Small Methods

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Practitioners still need to understand
the concepts of software design
Disclaimer #2
Code Smells Design Patterns
SOLID
Refactoring
Encapsulation
GRASP
Connascence

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Microtests are litmus tests
for software design quality

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Examples
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Too Much Test Setup
Too Many Dependencies Too Many Arguments
Arguments are Too Complex Code Under Test Doing Too Much
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Multiple ‘Act’ Steps
Temporal Coupling
Exists
Complicated API
Client needs to know too
much about object under test
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Too Many Steps to
Invoke Method
Under Test

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Too Many Asserts
Returning too complex of a type
Method under test doing too much
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Too Many Test Cases
Too much branching logic
Method under test is
doing too much
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Client-First Design
TDD enables software design from a client’s perspective.
Leads to better designed interfaces between objects
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Refactoring into design yields a better design than Big Design Up Front
Requirements Design Code Test
Waterfall Mindset
Requirements Test Code
Design
(Refactor)
(Test-Driven) Agile Mindset
Slide courtesy of Mike Rieser (@MichaelRieser)
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Developer Workflow Benefits
Short, fast feedback cycles improve productivity

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Nearly instantaneous
feedback loops
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Fast Feedback Loops
key to developer
productivity & high
performing teams
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Resilient to Interruptions
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TDD-created Microtests are save states for system functionality
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BIG PROBLEM

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BIG PROBLEM
Great software is created by GREAT TEAMS not heroic, rockstar, 10X
developers working in isolation

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BIG PROBLEM
Software development is a communication game
Communication is the professional developer’s first order of
business. Perhaps you thought that ‘getting it working’ was the
first order of business for a professional developer. I hope by now,
however, this book has disabused you of that idea.
- Robert Martin, Clean Code

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System is always in a working state
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Tiny Validations
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GeePaw Hill – TDD & the Lump of Coding Fallacy
https://www.geepawhill.org/2018/04/14/tdd-the-lump-of-coding-fallacy/

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Mental Benefits of TDD
One of the hardest things to communicate about Test-Driven
Development is the mental state it puts you in…On the original C3
project…progress was steady and unhurried; because it was unhurried it
seemed slow, but looking back on how much we got done, it was clear
that despite the unhurried feeling progress was really fast.
“
”
Martin Fowler - Afterword - Kent Beck’s TDD By Example
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Concrete and visible progress on small incremental goals
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Achieving Profluence
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Little or no time spent in the
debugger or on repetitive,
time consuming manual
checks
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Learning TDD will help improve software design, developer
workflow, increases developer happiness, and it’s a lot of fun!
https://geepawhill.org
https://github.com/testdouble/contributing-tests/wiki
Test Double – Contributing Tests Wiki
Industrial Logic
eLearning
https://www.industriallogic.com/elearning/
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http://bit.ly/slalom-beyond-unit-testing

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Attributes
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• SOS - https://www.flickr.com/photos/itupictures/16654290295
• Darts - https://www.flickr.com/photos/mike-burns/374198933
• Quote - Nick Youngson CC BY-SA 3.0
• Silver Bullet - https://www.flickr.com/photos/moneymetals/34301000331
• Litmus test - https://commons.wikimedia.org/wiki/File:Blue_and_red_litmus_paper.JPG
• Self-operating napkin - https://upload.wikimedia.org/wikipedia/commons/8/88/Self-
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Beyond Unit Testing: The Real Value of Test-Driven Development - Slalom

Beyond Unit Testing: The Real Value of Test-Driven Development - Slalom

Anthony Sciamanna

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