Is Your Code Too SOLID?

This version does NOT include a talk transcript; version with transcript is here:
https://speakerdeck.com/sarahmei/is-your-code-too-solid-with-transcript

SOLID is a collection of five common object-oriented development principles collected into one handy acronym. Smart people recommend learning about it, and even the name sounds fantastic — who doesn’t want to write “solid” code? Clearly, you should strive to follow all five principles, all the time, in all of your code. Right? Well. Good object-oriented design is indeed helpful, but SOLID as a set of guiding principles really isn’t. Let’s break SOLID down and reveal the limitations of our current approach, and try to understand just how SOLID our code needs to be.

Transcript

1. S A R A H
   M E I
   W D C N Z
   2 0 1 5
   I S Y O U R C O D E TO O
   S O L I D ?
   https://www.flickr.com/photos/pie4dan/4567311801
   

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2. DevMynd
   S A R A H M E I
   C H I E F C O N S U LTA N T
   D E V M Y N D
   U N I T E D S TAT E S
   C H I E F O F BA L D E A G L E S
   A N D F R E E D O M
   
   http://world-map1.org/map1520769_0_0.htm
   http://www.coolholidaygraphics.com/flagday/glittergraphics/flagdayglitter2.gif
   https://www.devmynd.com/images/team/sarah-mei-cutout.png
   

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3. DevMynd
   

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4. C O D E BA S E S
   I WO R K O N
   N O R M A L C O D E BA S E S
   https://www.flickr.com/photos/pmarkham/5361277692
   

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5. AT
   F I R S T
   https://www.flickr.com/photos/jakerust/16661140289/
   

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6. https://www.flickr.com/photos/123638374@N08/14184697490
   

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7. https://www.flickr.com/photos/123638374@N08/14184697490
   

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8. DevMynd
   https://twitter.com/tenderlove/status/573907559871971328
   

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9. DevMynd
   https://twitter.com/tenderlove/status/573907559871971328
   

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10. DevMynd
    S A N D I M E T Z
    E X P E RT AT
    E V E RY T H I N G S E R I O U S LY, G E T I T
    A M A Z I N G B O O K
    http://www.sandimetz.com/ http://www.poodr.com/
    

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11. DevMynd
    S A N D I M E T Z
    E X P E RT AT
    E V E RY T H I N G S E R I O U S LY, G E T I T
    A M A Z I N G B O O K
    http://www.sandimetz.com/ http://www.poodr.com/
    

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12. D E S I G N
    D E C I D I N G
    H OW TO
    A R R A N G E C O D E
    https://www.flickr.com/photos/matley0/3616669592
    

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13. D E S I G N
    D E C I D I N G
    H OW TO
    A R R A N G E C O D E
    https://www.flickr.com/photos/matley0/3616669592
    

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14. O B J E C T- O R I E N T E D
    D E S I G N
    G R O U P I N G R E L AT E D
    F U N C T I O N A L I T Y I N O B J E C T S
    https://www.flickr.com/photos/mwanasimba/2901201955/
    

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15. DevMynd
    A L A N G UA G E F E AT U R E
    A WAY O F T H I N K I N G
    O B J E C T- O R I E N T E D D E S I G N I S
    
    https://www.flickr.com/photos/56627607@N05/15635620289/
    

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16. DevMynd
    A L A N G UA G E F E AT U R E
    A WAY O F T H I N K I N G
    O B J E C T- O R I E N T E D D E S I G N I S
    A D E S T I N AT I O N
    A M E A N S TO A N E N D
    
    
    
    https://www.flickr.com/photos/56627607@N05/15635620289/
    

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17. https://www.flickr.com/photos/redvers/532076662/
    

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18. https://www.flickr.com/photos/redvers/532076662/
    

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19. H I G H
    L OW
    H I G H
    L OW
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    

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20. H I G H
    L OW
    H I G H
    L OW
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    

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21. H I G H
    L OW
    H I G H
    L OW
    Procedures
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    

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22. H I G H
    L OW
    H I G H
    L OW
    Procedures
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    

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23. CalendarParamMgr
    GetCalendarIndex
    CalendarRouteResolver
    CalendarRouteResolverFactory
    RouteResolver
    RouteReceiver
    

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24. H I G H
    L OW
    H I G H
    L OW
    Procedures
    Set of Small Objects
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    

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25. H I G H
    L OW
    H I G H
    L OW
    Procedures
    ⚠⚡
    Set of Small Objects
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    

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26. H I G H
    L OW
    H I G H
    L OW
    Procedures
    Set of Small Objects
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    Really big objects
    
    

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27. H I G H
    L OW
    H I G H
    L OW
    Procedures
    Set of Small Objects
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    Really big objects
    
    The wrong set
    of small objects
    
    

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28. H I G H
    L OW
    H I G H
    Procedures
    
    Set of Small Objects
    L OW
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    Really big objects
    
    The wrong set
    of small objects
    
    

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29. H I G H
    L OW
    H I G H
    Procedures
    
    Set of Small Objects
    L OW
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    Really big objects
    
    The wrong set
    of small objects
    
    

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30. PAT T E R N S
    https://www.flickr.com/photos/dakluza/6665460621
    

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31. O B S E R V E R
    N E W E M A I L
    User
    
    

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32. O B S E R V E R
    User UserObserver
    
    
    

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33. O B S E R V E R
    User UserObserver
    
    
    ! E M A I L
    N E W
    

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34. H I G H
    L OW
    H I G H
    
    L OW
    
    E A S I E R TO
    C H A N G E
    H A R D E R TO
    U N D E R S TA N D
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    

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35. https://www.flickr.com/photos/betsyweber/5902421276
    

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36. https://www.flickr.com/photos/grungetextures/4162992874
    

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37. S O L I D
    https://www.flickr.com/photos/chrisjfry/309574260/
    

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38. N A M E S U M M A RY U T I L I T Y
    S
    O
    L
    I
    D
    

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39. S I N G L E R E S P O N S I B I L I T Y
    P R I N C I P L E
    S O L I D
    https://www.flickr.com/photos/shenamt/8582808329/
    

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40. N A M E S U M M A RY U T I L I T Y
    S S I N G L E
    R E S P O N S I B I L I T Y
    O N E R E S P O N S I B I L I T Y
    P E R C L A S S
    M E D
    O
    L
    I
    D
    

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41. N A M E S U M M A RY U T I L I T Y
    S S I N G L E
    R E S P O N S I B I L I T Y
    O N E R E S P O N S I B I L I T Y
    P E R C L A S S
    M E D
    O
    L
    I
    D
    

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42. O P E N / C L O S E D
    P R I N C I P L E
    S O L I D
    https://www.flickr.com/photos/28481088@N00/4063800774/
    

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43. N A M E S U M M A RY U T I L I T Y
    S S I N G L E
    R E S P O N S I B I L I T Y
    O N E R E S P O N S I B I L I T Y
    P E R C L A S S
    M E D
    O O P E N / C L O S E D
    D O N ’ T E D I T C O D E ;
    A D D N E W C O D E
    L O W
    L
    I
    D
    

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44. L I S KOV S U B S T I T U T I O N
    P R I N C I P L E
    S O L I D
    https://www.flickr.com/photos/vpickering/14416940341/
    

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45. DevMynd
    Let Φ(x) be a property
    provable about objects x of
    type T. Then Φ(y) should be
    true for objects y of type S
    where S is a subtype of T.
    

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46. L I S KOV S U B S T I T U T I O N
    P R I N C I P L E
    S O L I D
    https://www.flickr.com/photos/vpickering/14416940341/
    

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47. I T ’ S N E V E R
    TO O L AT E TO
    https://www.flickr.com/photos/wcouch/8578612563/
    

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48. N A M E S U M M A RY U T I L I T Y
    S S I N G L E
    R E S P O N S I B I L I T Y
    O N E R E S P O N S I B I L I T Y
    P E R C L A S S
    M E D
    O O P E N / C L O S E D
    D O N ’ T E D I T C O D E ;
    A D D N E W C O D E
    L O W
    L L I S K O V
    S U B S T I T U T I O N
    I N H E R I TA N C E . I T ’ S A
    T H I N G .
    L O W
    I
    D
    

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49. I N T E R FA C E
    S E G R E G AT I O N
    P R I N C I P L E
    S O L I D
    https://www.flickr.com/photos/66126733@N04/8477516123/i
    

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50. W H Y S E G R E G AT E I N T E R FA C E S ?
    Musician
    AlbumCreator
    recordSong
    editSong
    mixSong
    sellMerch
    playSetList Gig
    

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51. W H Y S E G R E G AT E I N T E R FA C E S ?
    Musician
    AlbumCreator
    recordSong
    editSong
    mixSong
    sellMerch
    playSetList Gig
    driveVan
    
    
    
    

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52. W H Y S E G R E G AT E I N T E R FA C E S ?
    StudioActions
    AlbumCreator
    recordSong
    editSong
    mixSong
    sellMerch
    playSetList
    Gig
    driveVan
    VenueActions
    

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53. N A M E S U M M A RY U T I L I T Y
    S S I N G L E
    R E S P O N S I B I L I T Y
    O N E R E S P O N S I B I L I T Y
    P E R C L A S S
    M E D
    O O P E N / C L O S E D
    D O N ’ T E D I T C O D E ;
    A D D N E W C O D E
    L O W
    L L I S K O V
    S U B S T I T U T I O N
    I N H E R I TA N C E . I T ’ S A
    T H I N G .
    L O W
    I I N T E R FA C E
    S E G R E G AT I O N
    M A K E T H E A P I
    S M A L L
    H I G H
    D
    

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54. D E P E N D E N C Y I N V E R S I O N
    P R I N C I P L E
    S O L I D
    https://www.flickr.com/photos/hansmaulwurf/13702053625/
    

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55. N A M E S U M M A RY U T I L I T Y
    S S I N G L E
    R E S P O N S I B I L I T Y
    O N E R E S P O N S I B I L I T Y
    P E R C L A S S
    M E D
    O O P E N / C L O S E D
    D O N ’ T E D I T C O D E ;
    A D D N E W C O D E
    L O W
    L L I S K O V
    S U B S T I T U T I O N
    I N H E R I TA N C E . I T ’ S A
    T H I N G .
    L O W
    I I N T E R FA C E
    S E G R E G AT I O N
    M A K E T H E A P I
    S M A L L
    H I G H
    D D E P E N D E N C Y
    I N V E R S I O N
    M O V E C H O I C E S T O
    E D G E S O F S Y S T E M
    H I G H
    

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56. N A M E S U M M A RY U T I L I T Y
    S S I N G L E
    R E S P O N S I B I L I T Y
    O N E R E S P O N S I B I L I T Y
    P E R C L A S S
    M E D
    O O P E N / C L O S E D
    D O N ’ T E D I T C O D E ;
    A D D N E W C O D E
    L O W
    L L I S K O V
    S U B S T I T U T I O N
    I N H E R I TA N C E . I T ’ S A
    T H I N G .
    L O W
    I I N T E R FA C E
    S E G R E G AT I O N
    M A K E T H E A P I
    S M A L L
    H I G H
    D D E P E N D E N C Y
    I N V E R S I O N
    M O V E C H O I C E S T O
    E D G E S O F S Y S T E M
    H I G H
    

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57. N A M E S U M M A RY U T I L I T Y
    S S I N G L E
    R E S P O N S I B I L I T Y
    O N E R E S P O N S I B I L I T Y
    P E R C L A S S
    M E D
    O O P E N / C L O S E D
    D O N ’ T E D I T C O D E ;
    A D D N E W C O D E
    L O W
    L L I S K O V
    S U B S T I T U T I O N
    I N H E R I TA N C E . I T ’ S A
    T H I N G .
    L O W
    I I N T E R FA C E
    S E G R E G AT I O N
    M A K E T H E A P I
    S M A L L
    H I G H
    D D E P E N D E N C Y
    I N V E R S I O N
    M O V E C H O I C E S T O
    E D G E S O F S Y S T E M
    H I G H
    

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58. https://www.flickr.com/photos/29295318@N08/19322005453
    

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59. S T R AT E G Y &
    TA C T I C S
    https://www.flickr.com/photos/teegardin/6150427712/
    

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60. \ O /
    \ O /
    \ O /
    G OA L : P R O M O U N TA I N E E R
    S T R AT E G Y: C L I M B T H I S M T N
    TA C T I C S : T H E R O U T E U P
    https://www.flickr.com/photos/frenchy/222016256/
    

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61. \ O /
    \ O /
    \ O /
    G OA L : P R O M O U N TA I N E E R
    S T R AT E G Y: C L I M B T H I S M T N
    TA C T I C S : T H E R O U T E U P
    1
    2
    3
    https://www.flickr.com/photos/frenchy/222016256/
    

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62. G OA L : P R O M O U N TA I N E E R
    S T R AT E G Y: C L I M B T H I S M T N
    TA C T I C S : T H E R O U T E U P
    \ O /
    https://www.flickr.com/photos/frenchy/222016256/
    

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63. G OA L : P R O M O U N TA I N E E R
    S T R AT E G Y: C L I M B T H I S M T N
    https://www.flickr.com/photos/frenchy/222016256/
    

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64. G OA L : C H A N G E A B L E S O F T WA R E
    S T R AT E G Y:
    TA C T I C S :
    O O D E S I G N
    S O L I D
    https://www.flickr.com/photos/sunfox/5084875405/
    

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65. G OA L : C H A N G E A B L E S O F T WA R E
    S T R AT E G Y:
    TA C T I C S :
    O O D E S I G N
    S O L I D
    https://www.flickr.com/photos/sunfox/5084875405/
    

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66. N A M E S U M M A RY U T I L I T Y
    S S I N G L E
    R E S P O N S I B I L I T Y
    O N E R E S P O N S I B I L I T Y
    P E R C L A S S
    M E D
    O O P E N / C L O S E D
    D O N ’ T E D I T C O D E ;
    A D D N E W C O D E
    L O W
    L L I S K O V
    S U B S T I T U T I O N
    I N H E R I TA N C E . I T ’ S A
    T H I N G .
    L O W
    I I N T E R FA C E
    S E G R E G AT I O N
    M A K E T H E A P I
    S M A L L
    H I G H
    D D E P E N D E N C Y
    I N V E R S I O N
    M O V E C H O I C E S T O
    E D G E S O F S Y S T E M
    H I G H
    

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67. G OA L : C H A N G E A B L E S O F T WA R E
    S T R AT E G Y:
    TA C T I C S :
    S O L I D P R I N C I P L E S
    https://www.flickr.com/photos/sunfox/5084875405/
    

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68. G OA L : C H A N G E A B L E S O F T WA R E
    S T R AT E G Y:
    TA C T I C S :
    S O L I D P R I N C I P L E S
    https://www.flickr.com/photos/sunfox/5084875405/
    

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69. G OA L : C H A N G E A B L E S O F T WA R E
    S T R AT E G Y:
    TA C T I C S :
    S O L I D P R I N C I P L E S
    https://www.flickr.com/photos/sunfox/5084875405/
    

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70. https://www.flickr.com/photos/jonathancohen/15420956905
    

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71. H I G H
    L OW
    H I G H
    L OW
    The wrong set
    of small objects
    ❗
    C O S T O F U N D E R S TA N D I N G
    C O S T O F C H A N G E
    

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72. DevMynd
    T H E O N LY WAY TO M A K E A S TO P - T H E - WO R L D
    R E FA C TO R I N G WO R K I S TO N OT D O I T .
    http://www.imdb.com/title/tt0086567/
    

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73. https://www.flickr.com/photos/frenchy/222016256/
    

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74. https://www.flickr.com/photos/frenchy/222016256/
    

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75. DevMynd
    post.comments.first.author.email
    NOPE
    

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76. DevMynd
    https://www.flickr.com/photos/83794824@N07/8059223873/
    

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77. S TA B L E
    

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78. S TA B L E
    

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79. S TA B L E
    S M E L L Y O U R C O D E
    https://www.flickr.com/photos/pedrosimoes7/169983321/
    

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80. T I N Y P R O B L E M S
    F I R S T
    S TA B L E
    https://www.flickr.com/photos/ian-arlett/13706787684/
    

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81. S TA B L E
    https://www.flickr.com/photos/ian-arlett/13706787684/
    T I N Y P R O B L E M S
    F I R S T
    

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82. A U G M E N T T E S T S
    S TA B L E
    https://www.flickr.com/photos/horiavarlan/4273968004/
    

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83. https://www.flickr.com/photos/horiavarlan/4273968004/
    S TA B L E
    A U G M E N T T E S T S
    

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84. S TA B L E
    BA C K U P
    https://www.flickr.com/photos/mjonasson/19228720295/
    

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85. S TA B L E
    L E AV E I T
    B E T T E R T H A N
    Y O U F O U N D I T
    https://www.flickr.com/photos/spierisf/6989462184/
    

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86. https://www.flickr.com/photos/spierisf/6989462184/
    S TA B L E
    L E AV E I T
    B E T T E R T H A N
    Y O U F O U N D I T
    

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87. https://www.flickr.com/photos/spierisf/6989462184/
    S TA B L E
    L E AV E I T
    B E T T E R T H A N
    Y O U F O U N D I T
    

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88. E X P E C T
    G O O D
    R E A S O N S
    S TA B L E
    https://www.flickr.com/photos/an_untrained_eye/5012331537
    

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89. https://www.flickr.com/photos/an_untrained_eye/5012331537
    S TA B L E
    E X P E C T
    G O O D
    R E A S O N S
    

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90. S S M E L L Y O U R C O D E
    T T I N Y P R O B L E M S F I R S T
    A A U G M E N T T E S T S
    B B A C K U P
    L L E AV E I T B E T T E R
    E E X P E C T G O O D R E A S O N S
    

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91. S S M E L L Y O U R C O D E
    T T I N Y P R O B L E M S F I R S T
    A A U G M E N T T E S T S
    B B A C K U P
    L L E AV E I T B E T T E R
    E E X P E C T G O O D R E A S O N S
    

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92. DevMynd
    https://twitter.com/kentbeck/status/250733358307500032
    

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93. DevMynd
    https://twitter.com/kentbeck/status/250733358307500032
    

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94. https://www.flickr.com/photos/frenchy/222016256/
    

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95. \ O /
    https://www.flickr.com/photos/frenchy/222016256/
    

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96. https://www.flickr.com/photos/bevrichardmartin/5985876061/
    https://www.flickr.com/photos/discarnate/27211024/
    https://www.flickr.com/photos/lynardie/16191183291/
    

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97. DevMynd
    Sarah Mei
    sarah@devmynd.com
    @sarahmei
    THANK YOU!
    

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