Magic Tricks of Testing (AncientCityRuby)

@sandimetz Apr 2013 The Magic Tricks of Testing Sandi Metz
Friday, April 5, 13

@sandimetz Apr 2013 Why do I hate my tests? Friday,
April 5, 13

@sandimetz Apr 2013 They’re slow. Friday, April 5, 13

@sandimetz Apr 2013 They break every time I change something.
Friday, April 5, 13

@sandimetz Apr 2013 They cost more than they’re worth. Friday,
April 5, 13

@sandimetz Apr 2013 They are misery incarnate. Friday, April 5,
13

@sandimetz Apr 2013 It doesn’t have to be this way.
Friday, April 5, 13

@sandimetz Apr 2013 You just need to delete some tests.
Friday, April 5, 13

@sandimetz Apr 2013 Unit Tests: Goals Friday, April 5, 13

@sandimetz Apr 2013 Thorough Unit Tests: Goals Friday, April 5,
13

@sandimetz Apr 2013 Thorough Stable Unit Tests: Goals Friday, April
5, 13

@sandimetz Apr 2013 Thorough Stable Fast Unit Tests: Goals Friday,
April 5, 13

@sandimetz Apr 2013 Thorough Stable Fast Few Unit Tests: Goals
Friday, April 5, 13

@sandimetz Apr 2013 What does your app feel like? Friday,
April 5, 13

@sandimetz Apr 2013 Friday, April 5, 13

@sandimetz Apr 2013 Focus on messages. Friday, April 5, 13

@sandimetz Apr 2013 Objects have a simple understanding of messages.
Friday, April 5, 13

@sandimetz Apr 2013 Object Under Test Friday, April 5, 13

@sandimetz Apr 2013 Object Under Test Received from others Friday,
April 5, 13

@sandimetz Apr 2013 Object Under Test Incoming Friday, April 5,
13

@sandimetz Apr 2013 Sent to others Incoming Object Under Test
Friday, April 5, 13

@sandimetz Apr 2013 Incoming Outgoing Object Under Test Friday, April
5, 13

@sandimetz Apr 2013 Sent to self Incoming Outgoing Object Under
Test Friday, April 5, 13

@sandimetz Apr 2013 Incoming Sent to Self Outgoing Message Origin
Friday, April 5, 13

@sandimetz Apr 2013 Sent to self Incoming Outgoing Object Under
Test Friday, April 5, 13

@sandimetz Apr 2013 Sent to self Incoming Outgoing Query Command
Object Under Test Friday, April 5, 13

@sandimetz Apr 2013 Query Command Message Type Friday, April 5,
13

@sandimetz Apr 2013 Query: Returns something but changes nothing. Command:
Returns nothing but changes something. Type Friday, April 5, 13

@sandimetz Apr 2013 We conflate commands and queries at our
peril. Friday, April 5, 13

@sandimetz Apr 2013 But we do it all the time.
Friday, April 5, 13

@sandimetz Apr 2013 3 message Origins X 2 message Types
Friday, April 5, 13

Query Command Message Origin x Type Outgoing Incoming Type POV
@sandimetz Apr 2013 Message Sent to Self Friday, April 5, 13

@sandimetz GoGaRuCo 2012 @sandimetz Apr 2013 to Self Outgoing Incoming
Part 1 Incoming Friday, April 5, 13

Incoming Query Messages Incoming Friday, April 5, 13

Incoming Wheel diameter Friday, April 5, 13

class Wheel attr_reader :rim, :tire def initialize(rim, tire) # ... end def diameter rim + (tire * 2) end # ... Friday, April 5, 13

class WheelTest < MiniTest::Unit::TestCase def test_calculates_diameter wheel = Wheel.new(26, 1.5) assert_in_delta(29, wheel.diameter, 0.01) end end Friday, April 5, 13

@sandimetz Apr 2013 Rule Friday, April 5, 13

@sandimetz Apr 2013 Test incoming query messages Rule Friday, April
5, 13

@sandimetz Apr 2013 Test incoming query messages by making assertions
about what they send back. Rule Friday, April 5, 13

Query Command The Unit Testing Minimalist Incoming Type POV @sandimetz
Apr 2013 Message Sent to Self Outgoing Friday, April 5, 13

Query Command Assert result The Unit Testing Minimalist Incoming Type
POV @sandimetz Apr 2013 Message Sent to Self Outgoing Friday, April 5, 13

Incoming Another Incoming Query Message Friday, April 5, 13

Gear gear_inches Incoming Friday, April 5, 13

class Gear attr_reader :chainring, :cog, :wheel def initialize(args) # ... end # ... def gear_inches ratio * wheel.diameter end private def ratio chainring / cog.to_f end # ... end Friday, April 5, 13

class Gear attr_reader :chainring, :cog, :wheel def initialize(args) # ... end # ... def gear_inches ratio * wheel.diameter end private def ratio chainring / cog.to_f end # ... end Wheel Friday, April 5, 13

@sandimetz Apr 2013 Sight along the edges of the space
capsule. Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) end end Friday, April 5, 13

@sandimetz Apr 2013 Test the interface, Friday, April 5, 13

@sandimetz Apr 2013 Test the interface, not the implementation. Friday,
April 5, 13

Incoming Command Messages Incoming Friday, April 5, 13

Gear set_cog Incoming Friday, April 5, 13

class Gear attr_reader :chainring, :cog, :wheel def initialize(args) # ... end def set_cog(new_cog) @cog = new_cog end end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_set_cog gear = Gear.new gear.set_cog(27) assert(27, gear.cog) end end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_set_cog gear = Gear.new gear.set_cog(27) assert(27, gear.cog) end end Send the message Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_set_cog gear = Gear.new gear.set_cog(27) assert(27, gear.cog) end end Assert the side eﬀect Friday, April 5, 13

@sandimetz Apr 2013 Test incoming command messages Rule Friday, April
5, 13

@sandimetz Apr 2013 Test incoming command messages by making assertions
about direct public side eﬀects. Rule Friday, April 5, 13

POV @sandimetz Apr 2013 Message Sent to Self Outgoing Friday, April 5, 13

POV @sandimetz Apr 2013 Message Assert direct public side eﬀects Sent to Self Outgoing Friday, April 5, 13

@sandimetz Apr 2013 DRY It Out Friday, April 5, 13

@sandimetz Apr 2013 Receiver of incoming message has sole responsibility
DRY It Out Friday, April 5, 13

@sandimetz Apr 2013 Receiver of incoming message has sole responsibility
for asserting the result direct public side eﬀects. DRY It Out Friday, April 5, 13

Part 2 to Self Incoming Friday, April 5, 13

to Self Incoming Messages Sent to Self Friday, April 5, 13

class Gear # ... def gear_inches ratio * wheel.diameter end private def ratio chainring / cog.to_f end # ... end Friday, April 5, 13

Anti-Pattern to Self Incoming Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_ratio gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(4.7, gear.ratio, 0.01) end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_ratio gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(4.7, gear.ratio, 0.01) end Test the private method? Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_ratio gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(4.7, gear.ratio, 0.01) end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_ratio gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(4.7, gear.ratio, 0.01) end Redundant: Other tests already prove Gear works. Friday, April 5, 13

Friday, April 5, 13

Anti-Pattern to Self Incoming Friday, April 5, 13

class Gear # ... def gear_inches ratio * wheel.diameter end private def ratio chainring / cog.to_f end # ... end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) gear.expect(:ratio) gear.verify end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) gear.expect(:ratio) gear.verify end Expect to send the private method? Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) gear.expect(:ratio) gear.verify end Over Speci ed: Adds no safety yet breaks every time the implementation changes. Friday, April 5, 13

Friday, April 5, 13

@sandimetz Apr 2013 Do not test private methods. Rule Friday,
April 5, 13

@sandimetz Apr 2013 Do not test private methods. Do not
make assertions about their result. Rule Friday, April 5, 13

@sandimetz Apr 2013 Do not test private methods. Do not
make assertions about their result. Do not expect to send them. Rule Friday, April 5, 13

@sandimetz Apr 2013 Temporarily breaking this rule can save $$$
during development. Caveat Friday, April 5, 13

Query Command Assert result Assert direct public side-eﬀects The Unit
Testing Minimalist Incoming Type POV @sandimetz Apr 2013 Message Sent to Self Outgoing Friday, April 5, 13

Query Command Assert result Assert direct public side-eﬀects The Unit
Testing Minimalist Incoming Type POV @sandimetz Apr 2013 Ignore Message Sent to Self Outgoing Friday, April 5, 13

Part 3 Outgoing to Self Incoming Friday, April 5, 13

Outgoing to Self Incoming Outgoing Query Messages Friday, April 5, 13

Outgoing to Self Incoming Spoiler Alert Same rules as ‘Sent to Self’ Friday, April 5, 13

diameter Gear gear_inches Wheel Outgoing to Self Incoming Friday, April 5, 13

class Gear attr_reader :chainring, :cog, :wheel def initialize(args) # ... end def gear_inches ratio * wheel.diameter end private def ratio chainring / cog.to_f end # ... end Outgoing to Self Incoming Friday, April 5, 13

class Gear attr_reader :chainring, :cog, :wheel def initialize(args) # ... end def gear_inches ratio * wheel.diameter end private def ratio chainring / cog.to_f end # ... end Outgoing to Self Incoming Wheel Friday, April 5, 13

Gear Gear Outgoing Wheel diameter Incoming Query Outgoing to Self Incoming gear_inches Friday, April 5, 13

Anti-Pattern to Self Incoming Outgoing to Self Incoming Friday, April 5, 13

@sandimetz GoGaRuCo 2012 @sandimetz Apr 2013 to Self Incoming Outgoing

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) assert_in_delta(29, gear.wheel.diameter, 0.01) end end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) assert_in_delta(29, gear.wheel.diameter, 0.01) end end Assert result of outgoing query? Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) assert_in_delta(29, gear.wheel.diameter, 0.01) end end Redundant: This duplicates Wheel’s tests. Friday, April 5, 13

Friday, April 5, 13

Anti-Pattern to Self Incoming Outgoing to Self Incoming Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) gear.wheel.expect(:diameter) gear.verify end end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) gear.wheel.expect(:diameter) gear.verify end end Expect to send outgoing query? Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_calculates_gear_inches gear = Gear.new( chainring: 52, cog: 11, wheel: Wheel.new(26, 1.5)) assert_in_delta(137.1, gear.gear_inches, 0.01) gear.wheel.expect(:diameter) gear.verify end end Over Speci ed: Adds no safety yet breaks every time the implementation changes. Friday, April 5, 13

Friday, April 5, 13

@sandimetz Apr 2013 Rule Do not test outgoing query messages.
Friday, April 5, 13

Do not make assertions about their result. Friday, April 5, 13

Do not make assertions about their result. Do not expect to send them. Friday, April 5, 13

@sandimetz Apr 2013 If the message has no visible side-eﬀects
Friday, April 5, 13

@sandimetz Apr 2013 If the message has no visible side-eﬀects
the sender should not test it. Friday, April 5, 13

Query Command Assert result Assert direct public side eﬀects The
Unit Testing Minimalist Incoming Type POV @sandimetz Apr 2013 Message Ignore Sent to Self Outgoing Friday, April 5, 13

Outgoing Command Messages to Self Incoming Outgoing Friday, April 5, 13

diameter gear_inches set_cog changed to Self Incoming Outgoing Wheel Gear Obs Friday, April 5, 13

class Gear attr_reader :chainring, :cog, :wheel def initialize(args) # ... end def set_cog(new_cog) @cog = new_cog end end Change #set_cog to add observer. Friday, April 5, 13

class Gear attr_reader :chainring, :cog, :wheel def initialize(args) # ... end def set_cog(new_cog) @cog = new_cog end end Friday, April 5, 13

class Gear attr_reader :chainring, :cog, :wheel, :observer def initialize(args) # ... @observer = args[:observer] end def set_cog(new_cog) @cog = new_cog end end Friday, April 5, 13

class Gear # ... def set_cog(new_cog) @cog = new_cog end end Friday, April 5, 13

class Gear # ... def set_cog(new_cog) @cog = new_cog changed @cog end def changed observer.changed(chainring, cog) end end Friday, April 5, 13

Gear set_cog changed Obs to Self Incoming Outgoing Friday, April 5, 13

Gear set_cog changed Obs to Self Incoming Outgoing Side Effects Friday, April 5, 13

changed Gear set_cog Obs Incoming Command to Self Incoming Outgoing Side Effects Friday, April 5, 13

Gear Outgoing set_cog Obs changed Incoming Command to Self Incoming Outgoing Side Effects Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_set_cog gear = Gear.new gear.set_cog(27) assert(27, gear.cog) end end Make existing #set_cog test run. Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_set_cog gear = Gear.new @gear.set_cog(27) assert(27, @gear.cog) end end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_set_cog @observer = Obs.new gear = Gear.new @gear.set_cog(27) assert(27, @gear.cog) end end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_set_cog @observer = Obs.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @gear.set_cog(27) assert(27, @gear.cog) end end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_set_cog @observer = Obs.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @gear.set_cog(27) assert(27, @gear.cog) end end Runs real @observer#changed 1st version Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_set_cog @observer = Obs.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @observer.stub(:changed, @gear.set_cog(27)) do assert(27, @gear.cog) end end end Variant Runs fake @observer#changed Friday, April 5, 13

class Gear # ... def set_cog(new_cog) @cog = new_cog changed @cog end def changed observer.changed(chainring, cog) end end Friday, April 5, 13

class Gear # ... def set_cog(new_cog) @cog = new_cog changed @cog end def changed observer.changed(chainring, cog) end end The app will be correct only if this message gets sent. Friday, April 5, 13

@sandimetz GoGaRuCo 2012 @sandimetz Apr 2013 Wheel Incoming Query changed
Side Effects Gear Incoming Command Outgoing Obs Outgoing diameter gear_inches set_cog Friday, April 5, 13

@sandimetz GoGaRuCo 2012 @sandimetz Apr 2013 Side Effects Gear Wheel
Obs Friday, April 5, 13

Anti-Pattern to Self Incoming Outgoing Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_saves_changed_cog_in_db @observer = Obs.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @gear.set_cog(27) # assert something about the state of the db end end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_saves_changed_cog_in_db @observer = Obs.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @gear.set_cog(27) # assert something about the state of the db end end Depends on the distant side eﬀect. Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_saves_changed_cog_in_db @observer = Obs.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @gear.set_cog(27) # assert something about the state of the db end end Is this Gear’s responsibility? Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_saves_changed_cog_in_db @observer = Obs.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @gear.set_cog(27) # assert something about the state of the db end end This is an integration test. Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_notifies_observers_when_cogs_change @observer = MiniTest::Mock.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @observer.expect(:changed, true, [52, 27]) @gear.set_cog(27) @observer.verify end Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_notifies_observers_when_cogs_change @observer = MiniTest::Mock.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @observer.expect(:changed, true, [52, 27]) @gear.set_cog(27) @observer.verify end Depends on the interface. Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_notifies_observers_when_cogs_change @observer = MiniTest::Mock.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @observer.expect(:changed, true, [52, 27]) @gear.set_cog(27) @observer.verify end Gear is responsible for sending #changed to @observer. Friday, April 5, 13

@sandimetz Apr 2013 Expect to send outgoing command messages. Rule
Friday, April 5, 13

@sandimetz Apr 2013 Breaking this rule can save $$$ if
side eﬀects are both stable and cheap. Caveat Friday, April 5, 13

Query Command Assert result Assert direct public side eﬀects Ignore
The Unit Testing Minimalist Incoming Type POV @sandimetz Apr 2013 Message Ignore Sent to Self Outgoing Friday, April 5, 13

Expect to send The Unit Testing Minimalist Incoming Type POV @sandimetz Apr 2013 Message Ignore Sent to Self Outgoing Friday, April 5, 13

@sandimetz Apr 2013 But Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_notifies_observers_when_cogs_change @observer = MiniTest::Mock.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @observer.expect(:changed, true, [52, 27]) @gear.set_cog(27) @observer.verify end What happens if the Observer class stops implementing #changed? Friday, April 5, 13

@sandimetz Apr 2013 Stubs Friday, April 5, 13

@sandimetz Apr 2013 Stubs Stubs de ne context. Friday, April
5, 13

@sandimetz Apr 2013 Stubs Stubs de ne context. Stub as
needed (but zillions is a smell). Friday, April 5, 13

needed (but zillions is a smell). Avoid stubbing in the object under test. Friday, April 5, 13

needed (but zillions is a smell). Avoid stubbing in the object under test. Do not make assertions about stubs! Friday, April 5, 13

@sandimetz Apr 2013 Mocks Friday, April 5, 13

@sandimetz Apr 2013 Mocks Mocks test behavior. Friday, April 5,
13

@sandimetz Apr 2013 Mocks Mocks test behavior. Set expectations on
mocks to test outgoing command messages. Friday, April 5, 13

mocks to test outgoing command messages. One expectation per test (do your best). Friday, April 5, 13

mocks to test outgoing command messages. One expectation per test (do your best). Do not stub using a mock! Friday, April 5, 13

class GearTest < MiniTest::Unit::TestCase def test_notifies_observers_when_cogs_change @observer = MiniTest::Mock.new @gear = Gear.new( chainring: 52, cog: 11, observer: @observer) @observer.expect(:changed, true, [52, 27]) @gear.set_cog(27) @observer.verify end So really, what happens if Observer stops implementing #changed? Friday, April 5, 13

@sandimetz Apr 2013 Pain Friday, April 5, 13

@sandimetz Apr 2013 API Drift Pain Friday, April 5, 13

@sandimetz Apr 2013 Honor the contract. Rule Friday, April 5,
13

@sandimetz Apr 2013 Honor the contract. Ensure test doubles stay
in sync with the API. Rule Friday, April 5, 13

@sandimetz Apr 2013 Automagically minitest requires that stubbed methods exist
https://github.com/benmoss/quacky https://github.com/xaviershay/rspec-‐fire https://github.com/cfcosta/minitest-‐firemock Friday, April 5, 13

@sandimetz Apr 2013 Summary Friday, April 5, 13

@sandimetz Apr 2013 Strive for Thorough, Stable Fast, Few Friday,
April 5, 13

@sandimetz Apr 2013 Test. Friday, April 5, 13

@sandimetz Apr 2013 Test. Everything. Friday, April 5, 13

@sandimetz Apr 2013 Test . Everything. Once. Friday, April 5,
13

@sandimetz Apr 2013 Test the interface, Friday, April 5, 13

@sandimetz Apr 2013 Test the interface, not the implementation. Friday,
April 5, 13

@sandimetz Apr 2013 Guard against API drift. Friday, April 5,
13

Expect to send Be a Minimalist Incoming Type POV @sandimetz Apr 2013 Message Ignore Sent to Self Outgoing Friday, April 5, 13

@sandimetz Apr 2013 Use good judgement. Friday, April 5, 13

@sandimetz Apr 2013 Insist on simplicity. Friday, April 5, 13

@sandimetz Apr 2013 Practice the Tricks. Friday, April 5, 13

@sandimetz Apr 2013 And go home every day saying... Friday,
April 5, 13

@sandimetz Apr 2013 I love my tests. Friday, April 5,
13

Thanks Sandi Metz @sandimetz Friday, April 5, 13

http://www. ickr.com/photos/phil_shirley/5452562957/ thicket http://www. ickr.com/photos/zebble/6080622/ one padlock http://www. ickr.com/photos/chrisinplymouth/5543281168/ two
padlocks http://www. ickr.com/photos/donjohnson395/2915304926/ twins at beach http://www.med.navy.mil/sites/nmcp/Patients/pediatrics/PublishingImages/binocular_boy.gif http://upload.wikimedia.org/wikipedia/commons/e/e1/Ordinary_bicycle02.jpg ordinary bike Magic Hat (82805980) Copyright Mmaxer - Shutterstock.com Dogs in Hats (39263399) Copyright MLoiselle - Fotolia.com Garden (35521385) Copyright Beboy - Fotolia.com Space Walk - Nasa http://grin.hq.nasa.gov/copyright.html Photo Credits Friday, April 5, 13

@sandimetz Apr 2013 And one last time... http://poodr.info Friday, April
5, 13

@sandimetz Apr 2013 http://poodr.info Friday, April 5, 13

@sandimetz Apr 2013 Hot off the press http://poodr.info Friday, April
5, 13

Questions? Friday, April 5, 13

@sandimetz Apr 2013 http://poodr.info Friday, April 5, 13

Magic Tricks of Testing (AncientCityRuby)

Magic Tricks of Testing (AncientCityRuby)

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