Let's follow the white rabbit into a FizzBuzz refactoring story

1. What FizzBuzz can
teach us about design
"You take the red pill, you stay in
Wonderland and I show you
how deep the rabbit-hole goes"

2. TDD Training
and Design
and Refactoring

3. FizzBuzz + TDD

7. Nothing new

8. Nothing new
existing knowledge

9. Nothing new
existing knowledge
re-packaged in a way
that make sense to me

10. 1. Context
2. Code Katas

11. 1. Context

12. 1. Context
make observation on software
design at a micro level

13. 1. Context
make observation on software
design at a micro level
which is needed to be able to
evolve a codebase over time

14. 2. Code Katas

15. 2. Code Katas
Why? Am I wasting time?

16. 2. Code Katas
Why? Am I wasting time?
Perfect to practice a
technique in isolation

17. 2. Code Katas
Why? Am I wasting time?
Perfect to practice a
technique in isolation
Isolation allows to
improve more effectively

22. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

23. public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

24. public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}
public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

27. Change request

28. Change request
7 -> Bang

29. 3 -> Fizz
Change request

30. 3 -> Fizz
5 -> Buzz
Change request

31. 3 -> Fizz
5 -> Buzz
3&5 -> FizzBuzz
Change request

32. 3 -> Fizz 7 -> Bang
5 -> Buzz
3&5 -> FizzBuzz
Change request

33. 3 -> Fizz 7 -> Bang
5 -> Buzz
3&5 -> FizzBuzz 3&7 -> FizzBang
5&7 -> BuzzBang
3&5&7 -> ...
Change request

34. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}
Assess impact of change
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

35. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}
Assess impact of change
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

36. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}
Assess impact of change
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

37. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}
Assess impact of change
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

38. Change request
3,5 3 branches

39. Change request
3, 5, 7 7 branches
3,5 3 branches

40. Change request
3, 5, 7
3,5,7,11
7 branches
???
3,5 3 branches

41. Change request
3, 5, 7
3,5,7,11
7 branches
???
3,5 3 branches
19 branches

42. Surprised image?

43. Data change
Behaviour change
vs

44. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

45. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
} Not exactly the ideal design

46. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
} where do we start?
what do we do?

47. What do we do?

48. What do we do?
1. We implement the feature
and then refactor

49. What do we do?
1. We implement the feature
and then refactor
2. We refactor first and the
implement the feature

50. What do we do?
1. We implement the feature
and then refactor
2. We refactor first and the
implement the feature

51. Refactoring

52. Refactoring
1. Big Bang, tests broken till
the end (if you ever reach it)

53. Refactoring
1. Big Bang, tests broken till
the end (if you ever reach it)
2. Small safe steps, tests stay
green

55. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}
Assess impact of change
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

56. Challenge

57. Challenge
one line code change?

58. Challenge
one line code change?
no more if branches

59. Challenge
no more tests
one line code change?
no more if branches

60. Where do we start?

61. Where do we start?
Simplest code?

62. Where do we start?
Simplest code? More complex code?

63. Where do we start?
Simplest code? More complex code?
Top?

64. Where do we start?
Simplest code? More complex code?
Top? Bottom?

65. Where do we start?
Simplest code? More complex code?
Top? Bottom? Middle?

66. Where do we start?
Not a unique answer
Simplest code? More complex code?
Top? Bottom? Middle?

67. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

68. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "FizzBuzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

69. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

70. Evident Data
Reveal the intent of data making
their relationship evident

71. Too small to be
worth doing

72. Too small to be
worth doing

73. Refactoring session

74. Your plan
Refactoring session

75. Your plan
Refactoring session
Reality

76. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

77. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
var result = "";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

78. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
var result = "";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

79. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
var result = "";
if (num % 3 == 0)
return "Fizz";
if (num % 5 == 0)
return "Buzz";
return num.ToString();
}
}

80. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
return "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
return "Buzz";
}
return num.ToString();
}
}

81. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
return "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
return "Buzz";
}
if (result != "")
return result;
return num.ToString();
}

82. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
return "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
return "Buzz";
}
if (result != "")
return result;
return num.ToString();
}

83. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
return "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}

84. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
return "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}

85. public class FizzBuzzMachine
{
public string Say(int num)
{
if (num % 3 == 0 && num % 5 == 0)
return "Fizz"+"Buzz";
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}

86. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}

87. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}

88. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
Is it better?

89. Assess impact of change
public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

90. Assess impact of change
public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

91. Assess impact of change
public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

93. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

94. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}
data duplication between test and prod

95. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}
data duplication between test and prod
code duplication - if branches

96. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5 * 2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine();
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}
data duplication between test and prod
code duplication - if branches
primitive types

97. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}

98. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}

99. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
same code,
different data

100. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
same code,
different data

101. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (num % 3 == 0)
{
result += "Fizz";
}
if (num % 5 == 0)
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
}
Can we name the
intent of this code?

102. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (IsDivisible(num, 3))
{
result += "Fizz";
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor)
{
return num % divisor == 0;
}
}

103. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (IsDivisible(num, 3))
{
result += "Fizz";
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor)
{
return num % divisor == 0;
}
}
same code,
different data

104. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (IsDivisible(num, 3))
{
result += "Fizz";
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor)
{
return num % divisor == 0;
}
}
same code,
different data
Reconcile
differences

105. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
if (IsDivisible(num, 3))
{
result += "Fizz";
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor)
{
return num % divisor == 0;
}
}

106. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var fizzDivisor = 3;
if (IsDivisible(num, fizzDivisor))
{
result += "Fizz";
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor)
{
return num % divisor == 0;
}
}

107. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var fizzDivisor = 3;
var fizzWord = "Fizz";
if (IsDivisible(num, fizzDivisor))
{
result += fizzWord;
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

108. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var fizzDivisor = 3;
var fizzWord = "Fizz";
if (IsDivisible(num, fizzDivisor))
{
result += fizzWord;
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}
Data clump

109. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var fizzDivisor = 3;
var fizzWord = "Fizz";
var divAndWord = (Divisor: fizzDivisor, Word: fizzWord);
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

110. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var fizzDivisor = 3;
var fizzWord = "Fizz";
var divAndWord = (Divisor: fizzDivisor, Word: fizzWord);
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}
Ugly name

111. arlobelshee.com/tag/naming-is-a-process/

112. Design is

113. Design is
Structure and naming

114. Design is
Structure and naming
Goals

115. Design is
Structure and naming
Enable change
Goals

116. Design is
Structure and naming
Enable changeEnable unexpected change
Goals

117. Design is
Structure and naming
Enable change
Handle complexity
Enable unexpected change
Goals

118. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var fizzDivisor = 3;
var fizzWord = "Fizz";
var divAndWord = (Divisor: fizzDivisor, Word: fizzWord);
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

119. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var divAndWord = (Divisor: 3, Word: "Fizz");
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
if (IsDivisible(num, 5))
{
result += "Buzz";
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

120. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var divAndWord = (Divisor: 3, Word: "Fizz");
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
var divAndWord2 = (Divisor: 5, Word: "Buzz");
if (IsDivisible(num, divAndWord2.Divisor))
{
result += divAndWord2.Word;
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

121. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var divAndWord = (Divisor: 3, Word: "Fizz");
var divAndWord2 = (Divisor: 5, Word: "Buzz");
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
if (IsDivisible(num, divAndWord2.Divisor))
{
result += divAndWord2.Word;
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

122. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var divAndWord = (Divisor: 3, Word: "Fizz");
var divAndWord2 = (Divisor: 5, Word: "Buzz");
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
if (IsDivisible(num, divAndWord2.Divisor))
{
result += divAndWord2.Word;
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}
Same code, multiple data suggests...

123. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var divAndWord = (Divisor: 3, Word: "Fizz");
var divAndWord2 = (Divisor: 5, Word: "Buzz");
var divAndWords = new [] {divAndWord};
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
if (IsDivisible(num, divAndWord2.Divisor))
{
result += divAndWord2.Word;
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

124. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var divAndWord = (Divisor: 3, Word: "Fizz");
var divAndWord2 = (Divisor: 5, Word: "Buzz");
var divAndWords = new [] {divAndWord};
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
}
if (IsDivisible(num, divAndWord2.Divisor))
{
result += divAndWord2.Word;
}
if (result != "")
return result;
return num.ToString();
}

125. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var divAndWord = (Divisor: 3, Word: "Fizz");
var divAndWord2 = (Divisor: 5, Word: "Buzz");
var divAndWords = new [] {divAndWord};
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (IsDivisible(num, divAndWord2.Divisor))
{
result += divAndWord2.Word;
}
if (result != "")
return result;
return num.ToString();
}

126. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var divAndWord = (Divisor: 3, Word: "Fizz");
var divAndWord2 = (Divisor: 5, Word: "Buzz");
var divAndWords = new [] {divAndWord, divAndWord2};
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

127. public class FizzBuzzMachine
{
public string Say(int num)
{
var result = "";
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

128. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

129. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

130. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}
Abstraction in code
Details in metadata

131. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}
Feature Envy

132. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}
Primitive type
Feature Envy

133. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
var divAndWords2 = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;

134. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
var divAndWords2 = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;
Parallel
implementation

135. public class DivisorAndWord
{
public int Divisor { get; }
public string Word { get; }
public DivisorAndWord(int divisor, string word)
{
Divisor = divisor;
Word = word;
}
}

136. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
var divAndWords2 = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;

137. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
(Divisor: 3, Word: "Fizz"),
(Divisor: 5, Word: "Buzz")
};
var divAndWords2 = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords2)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;

138. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords2 = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWordItem in divAndWords2)
{
if (IsDivisible(num, divAndWordItem.Divisor))
{
result += divAndWordItem.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

139. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

140. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

141. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}

142. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
}
if (result != "")
return result;
return num.ToString();
}
static bool IsDivisible(int num, int divisor) {...}
}
Implicit else branch

143. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
if (IsDivisible(num, divAndWord.Divisor))
{
result += divAndWord.Word;
}
else
{
result += "";
}
}
if (result != "")
return result;
return num.ToString();

144. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
var word = "";
if (IsDivisible(num, divAndWord.Divisor))
{
word = divAndWord.Word;
result += divAndWord.Word;
}
else
{
word = "";
result += "";
}
}
if (result != "")

145. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
var word = "";
if (IsDivisible(num, divAndWord.Divisor))
{
word = divAndWord.Word;
result += word;
}
else
{
word = "";
result += word;
}
}
if (result != "")

146. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
var word = "";
if (IsDivisible(num, divAndWord.Divisor))
{
word = divAndWord.Word;
}
else
{
word = "";
}
result += word;
}
if (result != "")
return result;

147. public class FizzBuzzMachine
{
...
static string EvaluateAndGetWordOrEmpty(
int num, DivisorAndWord divAndWord)
{
string word;
if (IsDivisible(num, divAndWord.Divisor))
{
word = divAndWord.Word;
}
else
{
word = "";
}
return word;
}
...
}

148. public class DivisorAndWord
{
public int Divisor { get; }
public string Word { get; }
public DivisorAndWord(int divisor, string word)
{
Divisor = divisor;
Word = word;
}
public string EvaluateAndGetWordOrEmpty(int num)
{
if (IsDivisible(num, Divisor))
return Word;
else
return "";
}
public static bool IsDivisible(int num, int divisor)
{
return num % divisor == 0;
}
}

149. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}

150. public class FizzBuzzMachine
{
public string Say(int num)
{
var divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}

151. public class FizzBuzzMachine
{
DivisorAndWord[] divAndWords;
public FizzBuzzMachine()
{
this.divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
}
public string Say(int num)
{
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}

152. public class FizzBuzzMachine
{
DivisorAndWord[] divAndWords;
public FizzBuzzMachine()
{
this.divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
}
public string Say(int num)
{
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}
Push data up and
behaviour down

153. public class FizzBuzzMachine
{
DivisorAndWord[] divAndWords;
public FizzBuzzMachine(DivisorAndWord[] divAndWords)
{
this.divAndWords = divAndWords;
}
public string Say(int num)
{
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}

154. public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3*2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5*2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}
Let's review the
tests...

155. public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3*2));
}
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5*2));
}
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}
Let's review the
tests...

156. public class FizzBuzzTest
{
...
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
...
}

157. public class FizzBuzzTest
{
...
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
...
}

158. public class FizzBuzzTest
{
...
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
...
}

159. public class FizzBuzzTest
{
...
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
...
}
Input-output correlation

160. public class FizzBuzzTest
{
...
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
...
}
Input-output correlation

161. public class FizzBuzzTest
{
...
[Fact]
public void Fizz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
...
}
Input-output correlation
No hard-coded data in prod

162. public class FizzBuzzTest
{
...
[Fact]
public void SingleMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
...
}

163. public class FizzBuzzTest
{
...
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5*2));
}
...
}

164. public class FizzBuzzTest
{
...
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5*2));
}
...
}

165. public class FizzBuzzTest
{
...
[Fact]
public void Buzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5*2));
}
...
}

166. public class FizzBuzzTest
{
...
[Fact]
public void SingleMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5*2));
}
...
}

167. public class FizzBuzzTest
{
...
[Fact]
public void SingleMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5*2));
}
...
}
Equivalent to SingleMatch
but with different data

168. public class FizzBuzzTest
{
...
[Fact]
public void SingleMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Buzz", fizzBuzz.Say(5));
Assert.Equal("Buzz", fizzBuzz.Say(5*2));
}
...
}
Equivalent to SingleMatch
but with different data

169. public class FizzBuzzTest
{
...
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

170. public class FizzBuzzTest
{
...
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

171. public class FizzBuzzTest
{
...
[Fact]
public void FizzBuzz()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

172. public class FizzBuzzTest
{
...
[Fact]
public void MultipleMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

173. public class FizzBuzzTest
{
[Fact]
public void SimpleNumber()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
...

174. public class FizzBuzzTest
{
[Fact]
public void NoMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
...

175. public class FizzBuzzTest
{
[Fact]
public void NoMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void SingleMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void MultipleMatches()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

176. public class FizzBuzzTest
{
[Fact]
public void NoMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void SingleMatch()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void MultipleMatches()
{
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
});
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

177. public class FizzBuzzTest
{
readonly DivisorAndWord[] divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
[Fact]
public void NoMatch()
{
var fizzBuzz = new FizzBuzzMachine(divAndWords);
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void SingleMatch()
{
var fizzBuzz = new FizzBuzzMachine(divAndWords);
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void MultipleMatches()
{
var fizzBuzz = new FizzBuzzMachine(divAndWords);
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

178. Assess impact of change
public class FizzBuzzMachine
{
DivisorAndWord[] divAndWords;
public FizzBuzzMachine(Div...[] divAndWords)
{
this.divAndWords = divAndWords;
}
public string Say(int num)
{
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord
.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}
public class FizzBuzzTest
{
readonly DivisorAndWord[] divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
[Fact]
public void NoMatch()
{
var fizzBuzz = new FizzBuzzMachine(divAndWords);
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void SingleMatch()
{
var fizzBuzz = new FizzBuzzMachine(divAndWords);
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void MultipleMatches()
{
var fizzBuzz = new FizzBuzzMachine(divAndWords);
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}

179. Assess impact of change
public class FizzBuzzMachine
{
DivisorAndWord[] divAndWords;
public FizzBuzzMachine(Div...[] divAndWords)
{
this.divAndWords = divAndWords;
}
public string Say(int num)
{
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord
.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}
public class FizzBuzzTest
{
readonly DivisorAndWord[] divAndWords = new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz")
};
[Fact]
public void NoMatch()
{
var fizzBuzz = new FizzBuzzMachine(divAndWords);
Assert.Equal("1", fizzBuzz.Say(1));
Assert.Equal("2", fizzBuzz.Say(2));
}
[Fact]
public void SingleMatch()
{
var fizzBuzz = new FizzBuzzMachine(divAndWords);
Assert.Equal("Fizz", fizzBuzz.Say(3));
Assert.Equal("Fizz", fizzBuzz.Say(3 * 2));
}
[Fact]
public void MultipleMatches()
{
var fizzBuzz = new FizzBuzzMachine(divAndWords);
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5));
Assert.Equal("FizzBuzz", fizzBuzz.Say(3 * 5 * 2));
}
}
No changes here

180. Assess impact of change
public class FizzBuzzMachine
{
DivisorAndWord[] divAndWords;
public FizzBuzzMachine(Div...[] divAndWords)
{
this.divAndWords = divAndWords;
}
public string Say(int num)
{
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord
.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}
static void Main(string[] args)
{
Console.WriteLine("Welcome to FizzBuzz");
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz"),
});
for (int i = 1; i < 1000; i++)
{
var result = fizzBuzz.Say(i);
Console.Write($"{result} ");
}
}

181. Assess impact of change
public class FizzBuzzMachine
{
DivisorAndWord[] divAndWords;
public FizzBuzzMachine(Div...[] divAndWords)
{
this.divAndWords = divAndWords;
}
public string Say(int num)
{
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord
.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}
static void Main(string[] args)
{
Console.WriteLine("Welcome to FizzBuzz");
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz"),
});
for (int i = 1; i < 1000; i++)
{
var result = fizzBuzz.Say(i);
Console.Write($"{result} ");
}
}

182. Assess impact of change
public class FizzBuzzMachine
{
DivisorAndWord[] divAndWords;
public FizzBuzzMachine(Div...[] divAndWords)
{
this.divAndWords = divAndWords;
}
public string Say(int num)
{
var result = "";
foreach (var divAndWord in divAndWords)
{
result += divAndWord
.EvaluateAndGetWordOrEmpty(num);
}
if (result != "")
return result;
return num.ToString();
}
}
static void Main(string[] args)
{
Console.WriteLine("Welcome to FizzBuzz");
var fizzBuzz = new FizzBuzzMachine(new[]
{
new DivisorAndWord(3, "Fizz"),
new DivisorAndWord(5, "Buzz"),
new DivisorAndWord(7, "Bang")
});
for (int i = 1; i < 1000; i++)
{
var result = fizzBuzz.Say(i);
Console.Write($"{result} ");
}
}

185. What's next?

186. What's next?
Refactor foreach -> reduce
Better name for DivisorAndWord
Better name for EvaluateAndGetWordOrEmpty()
Maybe<Word> instead of empty string?

187. Wrap up

188. Wrap up
Push data up and
behaviour down
Parallel implementation Making the implicit, explicit
Abstraction in code
Details in metadata
Naming
Data clump
Reconcile differences
Evident data Refactoring in small safe steps
Design Data change vs
behaviour change

190. Massimo Iacolare
@iacoware

191. Massimo Iacolare
@iacoware
Thanks!