Below And
Beneath TDD
Test-Last Development and other
real world test patterns
Noel Rappin
@noelrap
Pathfinder Development
pathf.com
railsprescriptions.com

http://www.railsrx.com

TEST REFACTOR
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TEST REFACTOR
Why does testing work?
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Why does testing fail?
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What does it mean for
testing to “work”?
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Improve effectiveness
of team and
quality of code
NOT
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A perfect guarantee of
code correctness
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for me, tdd is about
confidence &
accountability &
responsibility & design &
reusability & portability &
flexibility & testing &
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trustworthiness &
teamwork & initiative &
flow & that's all i can
think of at the moment.
CODE
-- Kent Beck
Rx

TEST REFACTOR
Accurate view of code
Small, incremental steps
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Scaffold for change
Focus for development
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TEST REFACTOR
What does it mean for
testing to “fail”?
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Decrease efficiency and
code quality
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TEST REFACTOR
“It feels like there's a
hidden door that everyone
who tests has found and
walked through...
There are a bunch of us...
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that would love to join
the party, but don't know
where to find
the door.”
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TEST REFACTOR
If you are stuck in a
window or banging your
head against the wall,
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this will help
you get to the door
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TEST REFACTOR
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Test-Driven
Development
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AKA: Behavior-Driven
Development
or
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Test-First
Programming
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TDD Code has:
small pieces
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high cohesion
loose coupling
minimal side-effects
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TEST REFACTOR
☺Accurate view of code
☺Small, incremental steps
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☺Scaffold for change
☺Focus for development
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TEST REFACTOR
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TEST
Lose the refactoring
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TEST
Development, that
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happens
to have tests
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TEST
Symptoms:
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Increased duplicaton in
code.
Long methods
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TEST
Benefits:
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May seem faster at first
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TEST
Over time...
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TEST
☺Accurate view of code
Small, incremental steps
FAIL PASS
Scaffold for change
☺Focus for development
CODE Rx

TEST
Fix by:
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Cleaning up your mess
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TEST REFACTOR
FAIL PASS
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TEST REFACTOR
FAIL PASS
TEST
FAIL
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TEST REFACTOR
assert_equal(nil, actual) assert_equal(4.314, actual)
FAIL PASS
TEST
actual = 4.314
FAIL
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TEST REFACTOR
Data-Driven Testing
or
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Using your program
as a calculator
TEST
FAIL
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TEST REFACTOR
Benefits:
Failed Test Guaranteed
FAIL PASS
Value may be hard to
calculate TEST
FAIL
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TEST REFACTOR
Pitfalls:
Can mask ignorance
of domain
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Can lead to worse
TEST
problems
FAIL
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TEST REFACTOR
Accurate view of code
☺Small, incremental steps
FAIL PASS
☺Scaffold for change
☺Focus for development TEST
FAIL
CODE Rx

TEST REFACTOR
assert_equal(nil, actual) assert_equal(4.314, actual)
FAIL PASS
TEST
actual = 4.314
FAIL
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REFACTOR
CODE
actual = 4.314
assert_equal(4.314, actual)
PASS
TEST
Rx

CODE REFACTOR
Test-Next Development
aka
PASS
Code-Driven
Development
TEST
Rx

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Symptoms:
No more failing tests
Tweaking tests to
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match code
Coverage drop
TEST
Rx

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Benefits:
Useful when exploring
PASS
Useful when testing
views
TEST
Rx

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Pitfalls:
Easily slides into worse
patterns
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Hard to avoid
coverage gaps
TEST
Rx

CODE REFACTOR
Accurate view of code
☺Small, incremental steps
PASS
Scaffold for change
Focus for development
TEST
Rx

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Tautology Based
Development
PASS
TEST
Rx

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Definition:
Tests that can’t
PASS
fail
TEST
Rx

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Symptoms:
Bugs that should have
been covered
PASS
Mock object
misuse
TEST
Rx

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☹Accurate view of code
☺Small, incremental steps
PASS
Scaffold for change
☹Focus for development
TEST
Rx

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Mitigation:
Try to separate
code assertions
PASS
from application
data
TEST
Rx

CODE REFACTOR
PASS
TEST
Rx

CODE REFACTOR
CODE
CODE
CODE
PASS
CODE
CODE
CODE
TEST
Rx

CODE REFACTOR
CODE
CODE
CODE Test-Last Development PASS
CODE
CODE
CODE
TEST
Rx

CODE REFACTOR
CODE
Symptoms:
CODE
Significant coverage drop
CODE
PASS
Uncovered bugs
CODE
Harder to write tests
CODE
CODE
TEST
Rx

CODE REFACTOR
CODE
CODE This is one way in which
we talk past each other
CODE
PASS
Unit tests ≠ TDD
CODE
CODE
CODE
TEST
Rx

CODE REFACTOR
CODE Pitfall:
CODE Tests get more
CODE expensive
PASS
CODE Lower quality tests
CODE Programmer boredom
CODE
TEST
Rx

CODE REFACTOR
CODE
CODE Needed when:
CODE Hitting corner case PASS
CODE Dealing with legacy
CODE
CODE
TEST
Rx

CODE REFACTOR
CODE ☹Accurate view of code
CODE ☹Small, incremental steps
CODE
PASS
Scaffold for change
CODE
☹Focus for development
CODE
CODE
TEST
Rx

CODE REFACTOR
Escape by:
CODE
CODE Start the TDD process
CODE Don’t look back PASS
CODE Catch up to legacy
parts as you touch
CODE
them
CODE
TEST
Rx

CODE REFACTOR
CODE
CODE
CODE
PASS
CODE
CODE
CODE
TEST
Rx

CODE REFACTOR
CODE
CODE
CODE
Run
CODE
CODE
CODE
TEST
Rx

CODE REFACTOR
CODE
CODE
Coverage Driven
CODE Development Run
CODE
CODE
CODE
TEST
Rx

CODE REFACTOR
CODE
CODE
Symptom:
CODE
Run
Tests without assertions
CODE
CODE
CODE
TEST
Rx

CODE REFACTOR
CODE
Why?
CODE
Minimal approach to
CODE
Run
legacy
CODE
Hard to reach code
CODE
CODE
TEST
Rx

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CODE ☹Accurate view of code
CODE ☹Small, incremental steps
CODE
Run
☹Scaffold for change
CODE
☹Focus for development
CODE
CODE
TEST
Rx

TEST REFACTOR
FAIL PASS
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TEST REFACTOR
TEST TEST
TEST TEST
FAIL PASS
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TEST REFACTOR
TEST TEST
TEST TEST
Lots of Test
FAIL PASS
First Development
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TEST REFACTOR
TEST TEST
TEST TEST
Symptom:
FAIL PASS
Lots of test failures at
once during initial
developmment
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TEST REFACTOR
TEST TEST
TEST TEST
Benefit:
FAIL PASS
Allows planning for future
code
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TEST REFACTOR
TEST TEST
TEST TEST Cost:
Loss of focus
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Somewhat harder to
write code against
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TEST REFACTOR
TEST TEST
TEST TEST
Middle Ground:
FAIL PASS
RSpec pending
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TEST REFACTOR
TEST TEST
☺Accurate view of code
TEST TEST
Small, incremental steps
FAIL PASS
☺Scaffold for change
Focus for development
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TEST REFACTOR
FAIL PASS
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SETUP REFACTOR
TEST
PASS
FAIL
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SETUP REFACTOR
TEST
Setup Driven Development PASS
FAIL
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SETUP REFACTOR
Symptom:
TEST
Large, brittle setup
methods
PASS
Slow tests
FAIL
High-level tests
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SETUP REFACTOR
TEST
Costs:
PASS
This is why people
hate testing
FAIL
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SETUP REFACTOR
Accurate view of code
TEST
☹Small, incremental steps
PASS
☺Scaffold for change
Focus for development
FAIL
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SETUP REFACTOR
TEST
Escape by:
Mock Objects PASS
Real unit tests
FAIL
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TEST REFACTOR
FAIL PASS
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TEST REFACTOR
Another problem:
End to end failures
FAIL PASS
Lack of focus
Expectation failures
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Cucumber REFACTOR
TEST
A potential solution PASS
FAIL
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Cucumber REFACTOR
TEST Acceptance Test-Driven
PASS
Development
FAIL
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Cucumber REFACTOR
Symptom:
TEST
PASS
You are writing
acceptance tests
FAIL
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Cucumber REFACTOR
Costs:
TEST
PASS
Additional layer of test
code, indirection
FAIL
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Cucumber REFACTOR
Benefits:
TEST
PASS
Increased focus,
improved feedback
FAIL
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Cucumber REFACTOR
☺Accurate view of code
☺Small, incremental steps
TEST
PASS
☺Scaffold for change
☺Focus for development
FAIL
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TEST REFACTOR
FAIL PASS
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And So:
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TEST REFACTOR
Constant feedback
and
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baby steps
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TEST REFACTOR
Focus on what
comes next
Failure Driven
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Development
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TEST REFACTOR
Good code has
small pieces
high cohesion
FAIL PASS
loose coupling
minimal side-effects
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Invisible cost of bugs
or
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Done vs. “Done Done”
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TEST REFACTOR
Go write
some tests!
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TEST REFACTOR
Rails Test Prescriptions
http://www.railsrx.com
Pathfinder Development
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http://www.pathf.com
http://www.pathf.com/blogs
@noelrap @railsrx
BoF: 9PM CODE
Wed Pavillion 9-10 Rx