Practical unit testing 2014

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

2. Unit Tests 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

3. #pracunittests Test Driven Development move on!

4. #pracunittests 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

5. #pracunittests 2004 @tenpn

6. #pracunittests 2004 @tenpn

7. Definitions

8. #pracunittests Unit TestSingle explicit assumption IMPORTANT functional/integration interchangable

9. #pracunittests Unit TestSingle explicit assumption Integration Test Many implicit assumptions IMPORTANT functional/integration interchangable

10. #pracunittests Qualities of Good Unit Tests Readable - why. up to speed. Maintainable - how. modify for iterating. Trustworthy - quick, deterministic. no external resources.

11. #pracunittests Qualities of Good Unit Tests Readable Readable - why. up to speed. Maintainable - how. modify for iterating. Trustworthy - quick, deterministic. no external resources.

12. #pracunittests Qualities of Good Unit Tests Readable Maintainable Readable - why. up to speed. Maintainable - how. modify for iterating. Trustworthy - quick, deterministic. no external resources.

13. #pracunittests Qualities of Good Unit Tests Readable Maintainable Trustworthy Readable - why. up to speed. Maintainable - how. modify for iterating. Trustworthy - quick, deterministic. no external resources.

14. Post Mortem

15. #pracunittests F1 2011 X360/PS3/PC PRODUCTION CODE => SUBSYSTEM CODE  HIGHLIGHT loc shipped 4+ previously

16. #pracunittests F1 2011 X360/PS3/PC • Isolated new subsystem PRODUCTION CODE => SUBSYSTEM CODE  HIGHLIGHT loc shipped 4+ previously

17. #pracunittests F1 2011 X360/PS3/PC • Isolated new subsystem • 502 tests, 6700 lines of test code PRODUCTION CODE => SUBSYSTEM CODE  HIGHLIGHT loc shipped 4+ previously

18. #pracunittests F1 2011 X360/PS3/PC • Isolated new subsystem • 502 tests, 6700 lines of test code • 6200 lines of production code PRODUCTION CODE => SUBSYSTEM CODE  HIGHLIGHT loc shipped 4+ previously

19. #pracunittests A Partial Succes PRODUCTION CODE => SUBSYSTEM CODE  HIGHLIGHT loc shipped 4+ previously

20. #pracunittests • Clean, re-usable code A Partial Succes PRODUCTION CODE => SUBSYSTEM CODE  HIGHLIGHT loc shipped 4+ previously

21. #pracunittests • Clean, re-usable code • Fewer bugs A Partial Succes PRODUCTION CODE => SUBSYSTEM CODE  HIGHLIGHT loc shipped 4+ previously

22. #pracunittests • Clean, re-usable code • Fewer bugs • Easy to optimise A Partial Succes PRODUCTION CODE => SUBSYSTEM CODE  HIGHLIGHT loc shipped 4+ previously

23. #pracunittests • Clean, re-usable code • Fewer bugs • Easy to optimise • At end, treacle-like progress A Partial Succes PRODUCTION CODE => SUBSYSTEM CODE  HIGHLIGHT loc shipped 4+ previously

24. Unit Test Anti-Patterns

25. #pracunittests 1/4: The Opaque Anti-Pattern types: light grey names: bold dark grey literals: red else: dark grey

26. #pracunittests // 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); } 1/4: The Opaque Anti-Pattern types: light grey names: bold dark grey literals: red else: dark grey

27. #pracunittests // 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 1/4: The Opaque Anti-Pattern types: light grey names: bold dark grey literals: red else: dark grey

28. #pracunittests 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); } types: light grey names: bold dark grey literals: red else: dark grey

31. #pracunittests Opaque: No Magic Literals break the rules when you need to!

32. #pracunittests Opaque: No Magic Literals void 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); } break the rules when you need to!

36. #pracunittests void 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); }

37. #pracunittests void 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); }

38. #pracunittests Opaque: Informative, Consistent Test Name

39. #pracunittests Opaque: Informative, Consistent Test Name void nameOfFunctionUnderTest_ContextOfTest_DesiredResultOfTest() {

40. #pracunittests Opaque: Informative, Consistent Test Name void nameOfFunctionUnderTest_ContextOfTest_DesiredResultOfTest() { void testBackwardsToNormalLeftwardsGradient() {

41. #pracunittests Opaque: Informative, Consistent Test Name void nameOfFunctionUnderTest_ContextOfTest_DesiredResultOfTest() { void void withDirection_Left_InvertsGradient() {

42. #pracunittests void withDirection_Left_InvertsGradient() { 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); }

43. #pracunittests void withDirection_Left_InvertsGradient() { 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); }

44. #pracunittests Opaque: Arrange-Act-Assert

45. #pracunittests Opaque: Arrange-Act-Assert void 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); }

50. #pracunittests The Opaque Anti-Pattern breathe at end!

51. #pracunittests The Opaque Anti-Pattern • Hard to see "how"? breathe at end!

52. #pracunittests The Opaque Anti-Pattern • Hard to see "how"? • Demystify magic literals breathe at end!

53. #pracunittests The Opaque Anti-Pattern • Hard to see "how"? • Demystify magic literals • Consistent informative test name breathe at end!

54. #pracunittests The Opaque Anti-Pattern • Hard to see "how"? • Demystify magic literals • Consistent informative test name • Arrange-Act-Assert breathe at end!

55. #pracunittests 2/4: The Wet Anti-Pattern RacingLineOffsets.setSignedDistanceToRacingLine(RacingLine, float) On refactoring

56. #pracunittests RacingLineOffsets.setSignedDistanceToRacingLine(RacingLine, float, int) 2/4: The Wet Anti-Pattern RacingLineOffsets On refactoring

57. #pracunittests RacingLineOffsets.setSignedDistanceToRacingLine(RacingLine, float, int) 2/4: The Wet Anti-Pattern > Test library build failed with 235 error(s) RacingLineOffsets On refactoring

58. #pracunittests 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); beyondOffsets.setSignedDistanceToRacingLine( RacingLine.eCenter, -someOffsetBeyondRacingLine); float rightRacingLineEdge = someRacingLineRadius - someOffsetBeyondRacingLine; beyondOffsets.setSignedDistanceToRacingLine( 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); }

59. #pracunittests 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); beyondOffsets.setSignedDistanceToRacingLine( RacingLine.eCenter, -someOffsetBeyondRacingLine); float rightRacingLineEdge = someRacingLineRadius - someOffsetBeyondRacingLine; beyondOffsets.setSignedDistanceToRacingLine( 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); } Not DRY

60. #pracunittests Wet: Helper Functions void getIdealOffset_WithinRacingLineEdge_ReturnsOffset() { float someRacingLineRadius = 10.0f; float someOffsetWithinRadius = someRacingLineRadius * 0.8f; ! RacingLineOffsets withinOffsets = CreateRacingLineOffsets( someRacingLineRadius, someOffsetWithinRadius); ! OffsetRequest idealRequest = m_raceBehaviour.getIdealOffset(withinOffsets); ! float idealRacingLineOffset = idealRequest.GetOffset(); TEST_EQUAL( idealRacingLineOffset, someOffsetWithinRadius); } void getIdealOffset_BeyondRacingLineEdge_ReturnsEdge() { float someRacingLineRadius = 10.0f; float someOffsetBeyondRacingLine = someRacingLineRadius + 1.0f; ! RacingLineOffsets beyondOffsets = CreateRacingLineOffsets( someRacingLineRadius, someOffsetBeyondRacingLine); ! OffsetRequest idealRequest = m_raceBehaviour.getIdealOffset(beyondOffsets); ! float idealRacingLineOffset = idealRequest.GetOffset(); TEST_EQUAL( idealRacingLineOffset, withinOffsets.RightEdge); }

63. #pracunittests Wet: Helper Functions void getIdealOffset_WithinRacingLineEdge_ReturnsOffset() { float someRacingLineRadius = 10.0f; float someOffsetWithinRadius = someRacingLineRadius * 0.8f; ! RacingLineOffsets withinOffsets = CreateRacingLineOffsets( someRacingLineRadius, someOffsetWithinRadius); ! OffsetRequest idealRequest = m_raceBehaviour.getIdealOffset(withinOffsets); ! test_tauOffsetEqual(idealRequest, someOffsetWithinRadius); } void getIdealOffset_BeyondRacingLineEdge_ReturnsEdge() { float someRacingLineRadius = 10.0f; float someOffsetBeyondRacingLine = someRacingLineRadius + 1.0f; ! RacingLineOffsets beyondOffsets = CreateRacingLineOffsets( someRacingLineRadius, someOffsetBeyondRacingLine); ! OffsetRequest idealRequest = m_raceBehaviour.getIdealOffset(beyondOffsets); ! test_racingLineOffsetEqual( idealRequest, withinOffsets.RightEdge); }

64. #pracunittests Wet: Helper Functions void getIdealOffset_WithinRacingLineEdge_ReturnsOffset() { float someRacingLineRadius = 10.0f; float someOffsetWithinRadius = someRacingLineRadius * 0.8f; ! RacingLineOffsets withinOffsets = CreateRacingLineOffsets( someRacingLineRadius, someOffsetWithinRadius); ! OffsetRequest idealRequest = m_raceBehaviour.getIdealOffset(withinOffsets); ! test_tauOffsetEqual(idealRequest, someOffsetWithinRadius); } void getIdealOffset_BeyondRacingLineEdge_ReturnsEdge() { float someRacingLineRadius = 10.0f; float someOffsetBeyondRacingLine = someRacingLineRadius + 1.0f; ! RacingLineOffsets beyondOffsets = CreateRacingLineOffsets( someRacingLineRadius, someOffsetBeyondRacingLine); ! OffsetRequest idealRequest = m_raceBehaviour.getIdealOffset(beyondOffsets); ! test_racingLineOffsetEqual( idealRequest, withinOffsets.RightEdge); }

65. #pracunittests The Wet Anti-Pattern breathe at end!

66. #pracunittests The Wet Anti-Pattern • Hard-to-maintain hacky tests? breathe at end!

67. #pracunittests The Wet Anti-Pattern • Hard-to-maintain hacky tests? • Keep production sensibilities in unit test code breathe at end!

68. #pracunittests The Wet Anti-Pattern • Hard-to-maintain hacky tests? • Keep production sensibilities in unit test code • Stay DRY with helper functions and custom asserts breathe at end!

69. #pracunittests The Wet Anti-Pattern • Hard-to-maintain hacky tests? • Keep production sensibilities in unit test code • Stay DRY with helper functions and custom asserts • Do not hide the call to the function under test breathe at end!

70. #pracunittests 3/4: The Deep Anti-Pattern > Test failed: > getOwnerAtOffset_WithOwner_ReferencesOwnerAtManyOffsets > With Assert: VehicleID 0 != 1 on introducing a bug chi == “kai”!

71. #pracunittests 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

74. #pracunittests 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); } >1 explicit assumption make it clear

75. #pracunittests Deep: One Assert Per Test void getOwnerAtOffset_WithOwnerAndNegativeOffset_ReturnsOwner() { float someNegativeOffset = -1.0f; ! float ownerAtNegativeOffset = m_ownedDescription.getOwnerAtOffset(someNegativeOffset); ! test_OwningVehicleIsEqualTo(ownerAtNegativeOffset, m_someOwnerID); } ! void getOwnerAtOffset_WithOwnerAndPositiveOffset_ReturnsOwner() { // *snip* }

76. #pracunittests > Test failed: > getOwnerAtOffset_WithOwnerAndNegativeOffset_ReturnsOwner > With Assert: VehicleID 0 != 1 > Test failed: > getOwnerAtOffset_WithOwnerAndPositiveOffset_ReturnsOwner > With Assert: VehicleID 0 != 1

77. #pracunittests The Deep Anti-Pattern breathe at end!

78. #pracunittests The Deep Anti-Pattern • Test failures not fully informative? breathe at end!

79. #pracunittests The Deep Anti-Pattern • Test failures not fully informative? • Too many explicit assumptions per test breathe at end!

80. #pracunittests The Deep Anti-Pattern • Test failures not fully informative? • Too many explicit assumptions per test • Minimise assumptions per test breathe at end!

81. #pracunittests 4/4: The Wide Anti-Pattern On introducing a bug in behaviour system

82. #pracunittests 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

83. #pracunittests // 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); }

86. #pracunittests // 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); } >0 implicit assumptions

91. #pracunittests Wide: Seams void DraftBehaviour.updateImpl(WorldInfo wi, HeatMap heatInOut); Game Code Inversion of Control Interfaces/virtual functions Mocking frameworks/helper classes

92. #pracunittests Wide: Seams void DraftBehaviour.updateImpl(WorldInfo wi, HeatMap heatInOut); class HeatMap { virtual void WriteHeat(float offset, float value) { … } } Game Code Inversion of Control Interfaces/virtual functions Mocking frameworks/helper classes

93. #pracunittests Wide: Seams void DraftBehaviour.updateImpl(WorldInfo wi, HeatMap heatInOut); class HeatMap { virtual void WriteHeat(float offset, float value) { … } } class MockHeatMap : HeatMap { override void WriteHeat(float offset, float value) { … } } Game Code Test Library Inversion of Control Interfaces/virtual functions Mocking frameworks/helper classes

94. #pracunittests Wide: Seams void DraftBehaviour.updateImpl(WorldInfo wi, HeatMap heatInOut); class HeatMap { virtual void WriteHeat(float offset, float value) { … } } class MockHeatMap : HeatMap { override void WriteHeat(float offset, float value) { … } } Game Code Test Library Inversion of Control Interfaces/virtual functions Mocking frameworks/helper classes

95. #pracunittests 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); }

98. #pracunittests The Wide Anti-Pattern breathe at end!

99. #pracunittests The Wide Anti-Pattern • False-negative test failures? breathe at end!

100. #pracunittests The Wide Anti-Pattern • False-negative test failures? • Many implicit assumptions breathe at end!

101. #pracunittests The Wide Anti-Pattern • False-negative test failures? • Many implicit assumptions • Isolate code with seams, to enable simple fake impostors breathe at end!

102. #pracunittests 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

103. #pracunittests Recap • Respect unit test source code as much as production source code Respect unit test quality as much as production code quality Write once, read many Only 1 explicit assumption As few as possible implicit assumptions

104. #pracunittests Recap • Respect unit test source code as much as production source code • Write once, read many Respect unit test quality as much as production code quality Write once, read many Only 1 explicit assumption As few as possible implicit assumptions

105. #pracunittests Recap • Respect unit test source code as much as production source code • Write once, read many • Only 1 explicit assumption Respect unit test quality as much as production code quality Write once, read many Only 1 explicit assumption As few as possible implicit assumptions

106. #pracunittests Recap • Respect unit test source code as much as production source code • Write once, read many • Only 1 explicit assumption • Minimise implicit assumptions Respect unit test quality as much as production code quality Write once, read many Only 1 explicit assumption As few as possible implicit assumptions

107. #pracunittests • andrew.fray@gmail.com • @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!

Practical unit testing 2014

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