Practical unit testing 2014

http://tinyurl.com/sf-rnt

http://spryfox.com/our-games/road-not-taken/ shut down wifi, skype. RECORD!

UnitTests

Practical

Andrew Fray, Spry Fox

Thank you for coming. This is Practical Unit Tests, and I’m Andrew Fray. My talk today is about how to structure your unit tests to aid iteration. We’re going to be looking in detail at my unit tests from a shipped AAA console project, the mistakes I made in writing them, and the concrete costs they caused. Then we’ll look at simple ways to avoid those costs in your own unit tests.!definitions Post mortem Anti-patterns

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Test Driven Development

move on!

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Backwards Is Forward: Making Better Games with Test-Driven Development

http://gdcvault.com/play/1013416/Backwards-Is-Forward-Making-Better

Sean Houghton, Noel Llopis

http://tinyurl.com/gddtdd

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2004

@tenpn

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2004

@tenpn

Definitions

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Unit TestSingle explicit assumption

IMPORTANT functional/integration interchangable

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Unit TestSingle explicit assumption

Integration TestMany implicit assumptions

IMPORTANT functional/integration interchangable

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Qualities of Good Unit Tests

Readable - why. up to speed. Maintainable - how. modify for iterating. Trustworthy - quick, deterministic. no external resources.

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Readable


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Readable

Maintainable


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Readable

MaintainableTrustworthy


PostMortem

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F1 2011 X360/PS3/PC

PRODUCTION CODE => SUBSYSTEM CODEHIGHLIGHT loc shipped 4+ previously

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F1 2011 X360/PS3/PC

• Isolated new subsystem


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F1 2011 X360/PS3/PC


• 502 tests, 6700 lines of test code


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F1 2011 X360/PS3/PC


• 502 tests, 6700 lines of test code

• 6200 lines of production code


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A Partial Succes


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• Clean, re-usable code

A Partial Succes


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• Fewer bugs

A Partial Succes


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• Fewer bugs

• Easy to optimise

A Partial Succes


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• Fewer bugs

• Easy to optimise

• At end, treacle-like progress

A Partial Succes


Unit TestAnti-Patterns

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1/4: The Opaque Anti-Pattern

types: light grey names: bold dark grey literals: red else: dark grey

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// in LinearDescriptionFixture… void testBackwardsToNormalLeftwardsGradient() { LinearDescription leftDesc = DefaultFlatLinearDescription() .withGradient(1f).withInitialValue(10.0f).withOffsetOrigin(0.0f) .withDirection(Direction.eLeft); TEST_GREATER(leftDesc.getValueAtOffset(-1.0f), 10.0f); }



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// in LinearDescriptionFixture… void testBackwardsToNormalLeftwardsGradient() { LinearDescription leftDesc = DefaultFlatLinearDescription() .withGradient(1f).withInitialValue(10.0f).withOffsetOrigin(0.0f) .withDirection(Direction.eLeft); TEST_GREATER(leftDesc.getValueAtOffset(-1.0f), 10.0f); } wat



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Opaque: Hard to see HOW

void testBackwardsToNormalLeftwardsGradient() { LinearDescription leftDesc = DefaultFlatLinearDescription() .withGradient(1f).withInitialValue(10.0f).withOffsetOrigin(0.0f) .withDirection(Direction.eLeft); TEST_GREATER(leftDesc.getValueAtOffset(-1.0f), 10.0f); }


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Opaque: No Magic Literals

break the rules when you need to!

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Opaque: No Magic Literalsvoid testBackwardsToNormalLeftwardsGradient() { float someValueAtOrigin = 10.0f; float someOrigin = 0.0f; float positiveGradient = 1.0f; float someLeftOfOrigin = someOrigin - 1.0f; !

LinearDescription leftDesc = DefaultFlatLinearDescription() .withGradient(positiveGradient).withInitialValue(someValueAtOrigin) .withOffsetOrigin(someOrigin).withDirection(Direction.eLeft); float valueToLeft = leftDesc.getValueAtOffset(someLeftOfOrigin); TEST_GREATER(valueToLeft, someValueAtOrigin); }


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void testBackwardsToNormalLeftwardsGradient() { float someValueAtOrigin = 10.0f; float someOrigin = 0.0f; float positiveGradient = 1.0f; float someLeftOfOrigin = someOrigin - 1.0f; !


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void testBackwardsToNormalLeftwardsGradient() { float someValueAtOrigin = 10.0f; float someOrigin = 0.0f; float positiveGradient = 1.0f; float someLeftOfOrigin = someOrigin - 1.0f; !


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Opaque: Informative, Consistent Test Name

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void nameOfFunctionUnderTest_ContextOfTest_DesiredResultOfTest() {

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void testBackwardsToNormalLeftwardsGradient() {

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void

void withDirection_Left_InvertsGradient() {

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void withDirection_Left_InvertsGradient() { float someValueAtOrigin = 10.0f; float someOrigin = 0.0f; float positiveGradient = 1.0f; float someLeftOfOrigin = someOrigin - 1.0f; !


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void withDirection_Left_InvertsGradient() { float someValueAtOrigin = 10.0f; float someOrigin = 0.0f; float positiveGradient = 1.0f; float someLeftOfOrigin = someOrigin - 1.0f; !


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Opaque: Arrange-Act-Assert

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Opaque: Arrange-Act-Assertvoid withDirection_Left_InvertsGradient() { float someValueAtOrigin = 10.0f; float someOrigin = 0.0f; float positiveGradient = 1.0f; LinearDescription increasingDesc = DefaultFlatLinearDescription() .withGradient(positiveGradient).withInitialValue(someValueAtOrigin) .withOffsetOrigin(someOrigin); !

LinearDescription leftDesc = increasingDesc.withDirection(Direction.eLeft); !

float someLeftOfOrigin = someOrigin - 1.0f; float valueToLeft = leftDesc.getValueAtOffset(someLeftOfOrigin); TEST_GREATER(valueToLeft, someValueAtOrigin); }

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The Opaque Anti-Pattern

breathe at end!

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The Opaque Anti-Pattern• Hard to see "how"?

breathe at end!

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• Demystify magic literals

breathe at end!

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• Consistent informative test name

breathe at end!

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• Consistent informative test name

• Arrange-Act-Assert

breathe at end!

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2/4: The Wet Anti-Pattern

RacingLineOffsets.setSignedDistanceToRacingLine(RacingLine, float)

On refactoring

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RacingLineOffsets.setSignedDistanceToRacingLine(RacingLine, float, int)


RacingLineOffsets

On refactoring

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RacingLineOffsets.setSignedDistanceToRacingLine(RacingLine, float, int)


> Test library build failed with 235 error(s)

RacingLineOffsets

On refactoring

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void getIdealOffset_BeyondRacingLineEdge_ReturnsEdge() {

float someRacingLineRadius = 10.0f;

float someOffsetBeyondRacingLine = someRacingLineRadius + 1.0f;

! RacingLineOffsets beyondOffsets = new RacingLineOffsets();

float leftRacingLineEdge =

-someRacingLineRadius - someOffsetBeyondRacingLine;

beyondOffsets.setSignedDistanceToRacingLine(

RacingLine.eLeftEdge, leftRacingLineEdge);


RacingLine.eCenter, -someOffsetBeyondRacingLine);

float rightRacingLineEdge =

someRacingLineRadius - someOffsetBeyondRacingLine;


RacingLine.eRightEdge, rightRacingLineEdge);

! OffsetRequest idealRequest =

m_raceBehaviour.getIdealOffset(beyondOffsets);

! float idealRacingLineOffset = idealRequest.GetOffset();

TEST_EQUAL(idealRacingLineOffset, someRacingLineRadius);

}

void getIdealOffset_WithinRacingLineEdge_ReturnsOffset() { float someRacingLineRadius = 10.0f; float someOffsetWithinRadius = someRacingLineRadius * 0.8f; ! RacingLineOffsets withinOffsets = new RacingLineOffsets(); float leftRacingLineEdge = -someRacingLineRadius - someOffsetWithinRadius; withinOfffsets.setSignedDistanceToRacingLine( RacingLine.eLeftEdge, leftRacingLineEdge); withinOffsets.setSignedDistanceToRacingLine( RacingLine.eCenter, -someOffsetWithinRadius); float rightRacingLineEdge = someRacingLineRadius - someOffsetWithinRadius; withinOffsets.setSignedDistanceToRacingLine( RacingLine.eRightEdge, rightRacingLineEdge); ! OffsetRequest idealRequest = m_raceBehaviour.getIdealOffset(withinOffsets); ! float idealRacingLineOffset = idealRequest.GetOffset(); TEST_EQUAL(idealRacingLineOffset, someOffsetWithinRadius); }

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float someOffsetBeyondRacingLine = someRacingLineRadius + 1.0f;

! RacingLineOffsets beyondOffsets = new RacingLineOffsets();

float leftRacingLineEdge =

-someRacingLineRadius - someOffsetBeyondRacingLine;


RacingLine.eLeftEdge, leftRacingLineEdge);


RacingLine.eCenter, -someOffsetBeyondRacingLine);

float rightRacingLineEdge =

someRacingLineRadius - someOffsetBeyondRacingLine;


RacingLine.eRightEdge, rightRacingLineEdge);

! OffsetRequest idealRequest =


! float idealRacingLineOffset = idealRequest.GetOffset();

TEST_EQUAL(idealRacingLineOffset, someRacingLineRadius);

}

void getIdealOffset_WithinRacingLineEdge_ReturnsOffset() { float someRacingLineRadius = 10.0f; float someOffsetWithinRadius = someRacingLineRadius * 0.8f; ! RacingLineOffsets withinOffsets = new RacingLineOffsets(); float leftRacingLineEdge = -someRacingLineRadius - someOffsetWithinRadius; withinOfffsets.setSignedDistanceToRacingLine( RacingLine.eLeftEdge, leftRacingLineEdge); withinOffsets.setSignedDistanceToRacingLine( RacingLine.eCenter, -someOffsetWithinRadius); float rightRacingLineEdge = someRacingLineRadius - someOffsetWithinRadius; withinOffsets.setSignedDistanceToRacingLine( RacingLine.eRightEdge, rightRacingLineEdge); ! OffsetRequest idealRequest = m_raceBehaviour.getIdealOffset(withinOffsets); ! float idealRacingLineOffset = idealRequest.GetOffset(); TEST_EQUAL(idealRacingLineOffset, someOffsetWithinRadius); }

Not DRY

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Wet: Helper Functionsvoid getIdealOffset_WithinRacingLineEdge_ReturnsOffset() {


float someOffsetWithinRadius =

someRacingLineRadius * 0.8f;

!

RacingLineOffsets withinOffsets = CreateRacingLineOffsets(

someRacingLineRadius, someOffsetWithinRadius);

!

OffsetRequest idealRequest =

m_raceBehaviour.getIdealOffset(withinOffsets);

!

float idealRacingLineOffset = idealRequest.GetOffset();

TEST_EQUAL(

idealRacingLineOffset, someOffsetWithinRadius);

}



float someOffsetBeyondRacingLine =

someRacingLineRadius + 1.0f;

!

RacingLineOffsets beyondOffsets = CreateRacingLineOffsets(

someRacingLineRadius, someOffsetBeyondRacingLine);

!



!


TEST_EQUAL(

idealRacingLineOffset, withinOffsets.RightEdge);

}

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!



!



!


TEST_EQUAL(


}





!



!



!


TEST_EQUAL(


}

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!



!



!


TEST_EQUAL(


}





!



!



!


TEST_EQUAL(


}

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!



!



!

test_tauOffsetEqual(idealRequest, someOffsetWithinRadius);

}





!



!



!

test_racingLineOffsetEqual(

idealRequest, withinOffsets.RightEdge);

}

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!



!



!

test_tauOffsetEqual(idealRequest, someOffsetWithinRadius);

}





!



!



!

test_racingLineOffsetEqual(

idealRequest, withinOffsets.RightEdge);

}

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The Wet Anti-Pattern

breathe at end!

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The Wet Anti-Pattern• Hard-to-maintain hacky tests?

breathe at end!

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• Keep production sensibilities in unit test code

breathe at end!

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• Stay DRY with helper functions and custom asserts

breathe at end!

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• Stay DRY with helper functions and custom asserts

• Do not hide the call to the function under test

breathe at end!

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3/4: The Deep Anti-Pattern

> Test failed: > getOwnerAtOffset_WithOwner_ReferencesOwnerAtManyOffsets > With Assert: VehicleID 0 != 1

on introducing a bug chi == “kai”!

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void getOwnerAtOffset_WithOwner_ReferencesOwnerAtManyOffsets() { VehicleID someOwnerID = (VehicleID)1; LinearDescription ownedDescription = DefaultFlatLinearDescription().withOwner(someOwnerID); !

float someNegativeOffset = -1.0f; float ownerAtNegativeOffset = ownedDescription.getOwnerAtOffset(someNegativeOffset); float somePositiveOffset = 1.0f; float ownerAtPositiveOffset = ownedDescription.getOwnerAtOffset(somePositiveOffset); !

test_OwningVehicleIsEqualTo(ownerAtNegativeOffset, someOwnerID); test_OwningVehicleIsEqualTo(ownerAtPositiveOffset, someOwnerID); }

make it clear

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make it clear

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make it clear

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>1 explicit

assumption

make it clear

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Deep: One Assert Per Testvoid getOwnerAtOffset_WithOwnerAndNegativeOffset_ReturnsOwner() { float someNegativeOffset = -1.0f; !

float ownerAtNegativeOffset = m_ownedDescription.getOwnerAtOffset(someNegativeOffset); !

test_OwningVehicleIsEqualTo(ownerAtNegativeOffset, m_someOwnerID); } !

void getOwnerAtOffset_WithOwnerAndPositiveOffset_ReturnsOwner() { // *snip* }

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> Test failed: > getOwnerAtOffset_WithOwnerAndNegativeOffset_ReturnsOwner > With Assert: VehicleID 0 != 1 > Test failed: > getOwnerAtOffset_WithOwnerAndPositiveOffset_ReturnsOwner > With Assert: VehicleID 0 != 1

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The Deep Anti-Pattern

breathe at end!

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• Test failures not fully informative?

breathe at end!

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• Too many explicit assumptions per test

breathe at end!

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• Too many explicit assumptions per test

• Minimise assumptions per test

breathe at end!

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4/4: The Wide Anti-Pattern

On introducing a bug in behaviour system

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4/4: The Wide Anti-Pattern

> Executed 613 test(s), 599 test(s) passed, 14 test(s) failed.

On introducing a bug in behaviour system

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// in DraftBehaviourFixture… void updateImpl_WithCarToDraft_PushesAIToBehindCar() { WorldInfo worldInfo = new WorldInfo(); float someDraftTargetVehicleOffset = 2.0f; // *snip* blackboard setup !

DraftBehaviour draft = new DraftBehaviour(); !

BehaviourSystem behaviourSystem = new BehaviourSystem(); behaviourSystem.addBehaviour(draft); !

behaviourSystem.updateWithBlackboard(worldInfo); !

MovementRequest draftMovement = behaviourSystem.getMovementRequest(); TEST_EQUAL(draftMovement.desiredRacingLineOffset, someDraftTargetVehicleOffset); }

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>0 implicit

assumptions

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Wide: Seamsvoid DraftBehaviour.updateImpl(WorldInfo wi, HeatMap heatInOut);

Game Code

Inversion of Control Interfaces/virtual functions Mocking frameworks/helper classes

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class HeatMap { virtual void WriteHeat(float offset, float value) { … } }

Game Code


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class MockHeatMap : HeatMap { override void WriteHeat(float offset, float value) { … } }

Game Code

Test Library


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class MockHeatMap : HeatMap { override void WriteHeat(float offset, float value) { … } }

Game Code

Test Library


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Wide: MockHeatMapvoid updateImpl_WithCarToDraft_PushesAIToBehindCar() { WorldInfo worldInfo = new WorldInfo(); float someDraftTargetVehicleOffset = 2.0f; // *snip* blackboard setup !

DraftBehaviour draft = new DraftBehaviour(); MockHeatMap mockMap = new MockHeatMap(); !

draft.updateImpl(worldInfo, mockMap); !

float draftOffsetWithHighestHeat = mockMap.getHighestHeatOffset(); TEST_EQUAL(draftOffsetWithHighestHeat, someDraftTargetVehicleOffset); }

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The Wide Anti-Pattern

breathe at end!

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The Wide Anti-Pattern• False-negative test failures?

breathe at end!

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• Many implicit assumptions

breathe at end!

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• Many implicit assumptions

• Isolate code with seams, to enable simple fake impostors

breathe at end!

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Recap

Respect unit test quality as much as production code quality Write once, read many Only 1 explicit assumption As few as possible implicit assumptions

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Recap• Respect unit test source code as much as

production source code


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• Write once, read many


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• Only 1 explicit assumption


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• Only 1 explicit assumption

• Minimise implicit assumptions


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• [email protected]

• @tenpn

• andrewfray.wordpress.com

• Roy Osherove: Art of Unit Testing www.artofunittesting.com

• Michael Feathers: Working Effectively with Legacy Code

• Steve Freeman & Nat Pryce: Growing Object-Orientated Software, Guided By Tests

Colour scheme by Miaka www.colourlovers.com/palette/444487/Curiosity_Killed

Feedback! Thank the CAs!

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Practical unit testing 2014