1
00:00:00,160 --> 00:00:00,200
"Xtreme TDD"

2
00:00:01,560 --> 00:00:01,600
Quentin Ducasse.

3
00:00:04,320 --> 00:00:06,200
-Hi. In this redo of week 2,

4
00:00:06,520 --> 00:00:08,640
what we are going to do
is to basically implement

5
00:00:08,960 --> 00:00:12,880
the same Counter as we did in week 1,
but exclusively from the debugger

6
00:00:13,200 --> 00:00:15,240
and from a test-driven perspective.

7
00:00:15,560 --> 00:00:17,400
So, let us see what this means.

8
00:00:17,720 --> 00:00:19,400
We will go and open System Browser.

9
00:00:19,720 --> 00:00:23,360
What we will do
is define the "Test" class first.

10
00:00:23,680 --> 00:00:26,560
This is the idea
of a test-driven development.

11
00:00:26,880 --> 00:00:28,400
So, save that.

12
00:00:28,720 --> 00:00:34,720
Now, we will write our first test,
so "testCounterIsSetAndRead".

13
00:00:35,040 --> 00:00:37,200
What will this test do?
It will create a Counter,

14
00:00:37,520 --> 00:00:40,400
so temporary variable "c",

15
00:00:40,720 --> 00:00:42,400
to which we will assign "Counter new".

16
00:00:42,720 --> 00:00:47,800
Then, we will assign 7 to the value
of the "count" instance variable.

17
00:00:48,120 --> 00:00:54,440
And then, we will check that "c count"
is indeed equal to 7.

18
00:00:54,760 --> 00:00:56,960
We can see that "Counter" is emphasized.

19
00:00:57,280 --> 00:01:00,640
We have not defined "count:",
we have not defined "count".

20
00:01:00,960 --> 00:01:04,200
Nothing should work, basically,
but we will see.

21
00:01:05,280 --> 00:01:08,320
"Unknown variable: Counter,
please correct."

22
00:01:08,640 --> 00:01:11,320
"Counter" would like
to define a new class,

23
00:01:11,640 --> 00:01:15,840
would like to define it
with the "count" instance variable.

24
00:01:16,160 --> 00:01:17,240
And press OK.

25
00:01:17,560 --> 00:01:20,760
You can see that we have got
our "Counter" class that is created there

26
00:01:21,080 --> 00:01:22,840
with the instance variable "count".

27
00:01:23,160 --> 00:01:24,520
And now, if we run our test,

28
00:01:24,840 --> 00:01:29,360
we can see that the method "count:"
has not been understood.

29
00:01:29,680 --> 00:01:30,800
So, this is the debugger

30
00:01:31,120 --> 00:01:33,080
and basically,
this is the execution stack,

31
00:01:33,400 --> 00:01:36,000
this is the body of the method
that is being executed,

32
00:01:36,320 --> 00:01:38,720
and those are the different variables.

33
00:01:39,040 --> 00:01:41,800
So, if I go to "a Counter",
you can see that...

34
00:01:42,120 --> 00:01:43,360
This is "a Counter"... "Raw"...

35
00:01:43,680 --> 00:01:45,600
You can see that "count"
is equal to "nil",

36
00:01:45,920 --> 00:01:47,080
because we have not set it up.

37
00:01:47,400 --> 00:01:50,320
So, we can click on the Create button

38
00:01:50,640 --> 00:01:52,320
to create the method "count:".

39
00:01:52,640 --> 00:01:53,640
Go to Counter,

40
00:01:54,800 --> 00:01:58,800
and what we will do is go to "accessing".

41
00:01:59,120 --> 00:01:59,880
OK.

42
00:02:00,960 --> 00:02:03,920
So, this is the set I would like,
so this is fine.

43
00:02:04,240 --> 00:02:05,760
I can press Proceed.

44
00:02:06,080 --> 00:02:09,600
Then, it does not understand
the next "count", the getter.

45
00:02:09,920 --> 00:02:12,160
So, we can create it. Counter.

46
00:02:12,480 --> 00:02:15,880
Once again, in the "accessing" protocol.

47
00:02:16,200 --> 00:02:17,360
OK.

48
00:02:17,680 --> 00:02:19,960
"Count", well written "count".
That is great.

49
00:02:20,280 --> 00:02:21,560
So, Proceed.

50
00:02:21,880 --> 00:02:24,640
The test is red,
but if we click on it, it is green.

51
00:02:24,960 --> 00:02:25,880
So, perfect.

52
00:02:26,200 --> 00:02:29,240
And if we go and have a look
at the "Counter" class,

53
00:02:29,560 --> 00:02:33,600
we now have our Setter and Getter
for the "count" instance variable,

54
00:02:33,920 --> 00:02:34,960
so that is perfect.

55
00:02:35,280 --> 00:02:37,920
Now, if you remember correctly,
we had a "class" method

56
00:02:38,240 --> 00:02:41,040
that had this
"choose the starting value",

57
00:02:41,360 --> 00:02:45,320
so we used it as "startingAt: 5".

58
00:02:45,640 --> 00:02:47,280
We will not need this line,

59
00:02:47,600 --> 00:02:52,160
but we would like to assert
that the count is indeed equal to 5.

60
00:02:52,480 --> 00:02:53,600
So, let us save this.

61
00:02:53,920 --> 00:02:56,160
It does not understand
the "startingAt" message,

62
00:02:56,480 --> 00:02:58,280
but we will define it right now.

63
00:02:58,600 --> 00:03:02,000
Click on it. "Instance of 'Counter' class
did not understand 'startingAt'".

64
00:03:02,320 --> 00:03:05,920
So, let us create it
in the "Counter" class,

65
00:03:06,240 --> 00:03:11,960
under the "instance creation" protocol.

66
00:03:12,280 --> 00:03:13,040
Press OK.

67
00:03:13,360 --> 00:03:15,720
And we will have to implement it,
so basically,

68
00:03:16,040 --> 00:03:18,120
what will "startingAt" do?

69
00:03:18,440 --> 00:03:21,320
It will create a counter:

70
00:03:21,640 --> 00:03:25,240
"c := Counter new."

71
00:03:25,560 --> 00:03:28,920
Then, it will assign
the value "anInteger"

72
00:03:29,240 --> 00:03:31,480
to the instance variable "count",

73
00:03:31,800 --> 00:03:33,840
and it will be written in this Counter.

74
00:03:34,160 --> 00:03:35,720
So, let us save this.

75
00:03:36,040 --> 00:03:37,520
Press Proceed.

76
00:03:37,840 --> 00:03:39,640
And you can see
that all of this is green.

77
00:03:39,960 --> 00:03:43,360
We still have some code there
that is not updated,

78
00:03:43,680 --> 00:03:45,720
but if I go back... There it is.

79
00:03:46,040 --> 00:03:48,640
Everything is understood
and everything is green.

80
00:03:48,960 --> 00:03:51,640
Now, another thing
that we would like to implement

81
00:03:51,960 --> 00:03:54,080
is the increment and decrement.

82
00:03:54,400 --> 00:03:57,400
So, "testCounterIncrement".

83
00:03:57,720 --> 00:04:03,280
We will go there
and do "increment; increment".

84
00:04:03,600 --> 00:04:06,360
And we would like "count"
to be equal to 7.

85
00:04:06,680 --> 00:04:08,120
So, let us save this.

86
00:04:08,440 --> 00:04:09,440
We will run it.

87
00:04:10,440 --> 00:04:12,080
"Increment" was not understood.

88
00:04:12,400 --> 00:04:14,400
This is normal,
since we have not defined it.

89
00:04:14,720 --> 00:04:16,600
So, go over to the Create button.

90
00:04:16,920 --> 00:04:17,680
We would like to create

91
00:04:18,000 --> 00:04:20,000
the method "increment"
in the "Counter" class,

92
00:04:20,320 --> 00:04:22,720
under the "operation" protocol.

93
00:04:23,040 --> 00:04:24,440
OK.

94
00:04:24,760 --> 00:04:25,680
"ShouldBeImplemented".

95
00:04:26,000 --> 00:04:28,000
So, what should our
"increment" method do?

96
00:04:28,320 --> 00:04:32,080
"count := count + 1".

97
00:04:32,400 --> 00:04:33,360
Save this.

98
00:04:33,680 --> 00:04:34,840
Press Proceed.

99
00:04:35,160 --> 00:04:37,080
Our method is green. That is cool.

100
00:04:37,400 --> 00:04:39,960
Now, we can do the same thing
with decrement.

101
00:04:41,440 --> 00:04:45,760
"Decrement", and there,
"testCounterDecrement".

102
00:04:46,080 --> 00:04:47,040
We will save it.

103
00:04:47,360 --> 00:04:48,600
Run this method.

104
00:04:49,800 --> 00:04:53,560
We have to create the method "decrement"
in the "Counter" class.

105
00:04:53,880 --> 00:04:55,480
Go to "operation".

106
00:04:57,040 --> 00:04:58,280
Press OK.

107
00:04:58,600 --> 00:04:59,440
Decrement.

108
00:04:59,760 --> 00:05:05,760
In the same way we created increment,
we will just do "count := - 1".

109
00:05:07,160 --> 00:05:08,160
We will save this.

110
00:05:08,480 --> 00:05:09,440
Press Proceed.

111
00:05:09,760 --> 00:05:13,000
Our test is not right
because I have not changed

112
00:05:13,320 --> 00:05:17,440
the actual value
I would like it to be equal to.

113
00:05:18,680 --> 00:05:21,240
I would like it to be equal to 3.

114
00:05:21,560 --> 00:05:23,440
So, I can change it right there
from the debugger.

115
00:05:23,760 --> 00:05:26,480
Press Cmd+S and press Proceed.

116
00:05:26,800 --> 00:05:28,840
And all our tests are green.

117
00:05:29,160 --> 00:05:33,840
And what you can see is we have only
basically developed a test,

118
00:05:34,160 --> 00:05:38,160
and we still have all the back-end
functionalities from the "Counter" class.

119
00:05:38,480 --> 00:05:41,000
So, "count", "count:",
"decrement", "increment",

120
00:05:41,320 --> 00:05:44,440
and everything is correctly organized.

121
00:05:44,760 --> 00:05:47,320
And all of this was made
from within the debugger.

122
00:05:47,640 --> 00:05:49,680
So, this is one of the strengths
of Pharo.

123
00:05:50,000 --> 00:05:51,320
The debugger is a work environment

124
00:05:51,640 --> 00:05:55,640
and you can really boost
your productivity by doing this.