A tour of @pragdave's Checkout kata, using connascence to guide the refactoring steps. Presented at Agile Manchester 2015.

1. Red, green,
… what now?!
@kevinrutherford
@jjeffries1

2. Primitive Obsession
Feature Envy
Sim
ulated
Polym
orphism
Lazy Class
Temporary Field
Inappropriate Intimacy
ShotgunSurgery
Data Clump
Long
M
ethod
Large Class
???
??? ???
???
???
???
???
RefusedBequest

3. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

4. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

5. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

6. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

7. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

8. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

9. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

10. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

11. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

12. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Connascence of ...

13. Scanning a
single item

15. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:

16. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:CoEO
scan()scan()

17. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
CoV
CoEO
scan()scan()
5050

18. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:CoEO
CoM
scan()scan()
int
int
int

19. Checkout with
an empty basket

21. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
CoM
int
int
int
unitPrice = 50
unitPrice = 50
int
CoA

22. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
CoM
int
int
int

23. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:

24. Different items
have different
prices

26. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
string string
CoM

27. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
string string
balance.add()
balance.add()
CoM
CoA

28. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
“A”“A”
string string
balance.add()
balance.add()
CoV
CoM
CoA

29. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
CoV
“A”“A”
3030
string string
balance.add()
balance.add()
CoV
CoM
CoA

30. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
“A”“A”
string string
balance.add()
balance.add()
CoV
CoM
CoA
Money, MoneyMoney, Money
CoP

31. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
string string
balance.add()
balance.add()
CoM
CoA
Money, MoneyMoney, Money
CoP

32. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:
string string
CoM
Map Map
CoM

33. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Test: Code:

34. Recap

35. Scanning a
single item

37. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Scanning has no
effect on the balance
Both classes know
the price = 50

38. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Introduce
Parameter{

39. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Scanning has no
effect on the balance
Everyone knows we use
an int to represent money

40. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Write a test{

41. Checkout with
an empty basket

43. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Everyone knows we use
an int to represent money
Common test
setup

44. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Introduce @Before
block{

45. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Everyone knows we use
an int to represent money

46. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Introduce Money class{

47. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9

48. Different items
have different
prices

50. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
balance.add()
called twice
Strings used to
represent product
codes
Everyone depends
on “A”
Everyone knows
the price of “B”

51. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Introduce
Parameter{

52. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
balance.add()
called twice
Strings used to
represent product
codes
Everyone depends
on “A”
Constructor parameters
are indistinguishable

53. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Introduce
Parameter{

54. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
balance.add()
called twice
Strings used to
represent product
codes
Constructor parameters
are indistinguishable

55. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Introduce a Map of
names to prices{

56. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Strings used to
represent product
codes
Map used to represent
the price list

57. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9
Introduce
PriceList{

58. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
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8
9
Introduce
ProductCode{

59. Name
Type
Meaning
Algorithm
Position
Execution Order
Timing
Value
Identity
1
2
3
4
5
6
7
8
9

60. Red, green,
… what now?!
@kevinrutherford
@jjeffries1