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+1
+00:00:00,320 --> 00:00:03,450
+Let's look at the code for PrintSum in a slightly different way
+
+2
+00:00:03,450 --> 00:00:06,140
+by making something explicit. If we go through the code, we can
+
+3
+00:00:06,140 --> 00:00:08,578
+see that the, the code does something in that case, if the
+
+4
+00:00:08,578 --> 00:00:11,720
+result greater then zero, does something else if the result is not
+
+5
+00:00:11,720 --> 00:00:14,890
+greater than zero but is less than zero, and otherwise in the
+
+6
+00:00:14,890 --> 00:00:17,800
+case in which neither of these two conditions is true. Nothing really
+
+7
+00:00:17,800 --> 00:00:19,090
+happens. So we're going to make that
+
+8
+00:00:19,090 --> 00:00:21,290
+explicit, we're going to say here, otherwise
+
+9
+00:00:21,290 --> 00:00:25,430
+do nothing, which is exactly our problem, the code does nothing, in this
+
+10
+00:00:25,430 --> 00:00:28,380
+case where it should do something. So now, let's look again in
+
+11
+00:00:28,380 --> 00:00:31,470
+our test cases, let's consider the first one, and I'm going to go a
+
+12
+00:00:31,470 --> 00:00:34,410
+little faster in this case, because we already saw what happens If
+
+13
+00:00:34,410 --> 00:00:37,890
+we execute the first test case, we get to this point, we execute
+
+14
+00:00:37,890 --> 00:00:40,710
+this statement, and then we just jump to the end, as we
+
+15
+00:00:40,710 --> 00:00:44,020
+saw. Now we, if we execute the second test case, we do the
+
+16
+00:00:44,020 --> 00:00:46,740
+same, we get to the else statement, the condition for the if is
+
+17
+00:00:46,740 --> 00:00:50,770
+true, and therefore we execute this statement. And we never reached this point
+
+18
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+for either of the test cases. So how can we express
+
+19
+00:00:53,320 --> 00:00:56,470
+this? In order to do that, I'm going to introduce a very useful
+
+20
+00:00:56,470 --> 00:01:00,450
+concept. The concept of control flow graphs. The control flow graphs
+
+21
+00:01:00,450 --> 00:01:03,310
+is just a representation for the code that is very convenient when
+
+22
+00:01:03,310 --> 00:01:06,030
+we run our reason about the code and its structure. And
+
+23
+00:01:06,030 --> 00:01:09,910
+it's a fairly simple one that represents statement with notes and the
+
+24
+00:01:09,910 --> 00:01:12,900
+flow of control within the code with edges. So here's an
+
+25
+00:01:12,900 --> 00:01:16,180
+example of control flow graph for this code. There is the entry
+
+26
+00:01:16,180 --> 00:01:19,790
+point of the code right here, then our statement in which we
+
+27
+00:01:19,790 --> 00:01:23,320
+assign the result of A plus B to variable result. Our if
+
+28
+00:01:23,320 --> 00:01:25,720
+statement and as you can see the if statement it's got two
+
+29
+00:01:25,720 --> 00:01:28,930
+branches coming out of it, because based on the outcome of this
+
+30
+00:01:28,930 --> 00:01:32,376
+predicate we will go one way or the other. In fact normally
+
+31
+00:01:32,376 --> 00:01:36,000
+what we do, we will label this edges accordingly. So for example,
+
+32
+00:01:36,000 --> 00:01:38,580
+here we will say that this is the label to be executed
+
+33
+00:01:38,580 --> 00:01:41,470
+when the predicate is true. And this is the label that is executed
+
+34
+00:01:41,470 --> 00:01:44,120
+when the predicate is false. Now, at this point, similar
+
+35
+00:01:44,120 --> 00:01:47,080
+thing, statement five which corresponds with this one, we have another
+
+36
+00:01:47,080 --> 00:01:49,650
+if statement and if that statement is true, then we get
+
+37
+00:01:49,650 --> 00:01:51,830
+to this point and if it's false, we get to this
+
+38
+00:01:51,830 --> 00:01:54,370
+point. So as you can see, this graph represents my
+
+39
+00:01:54,370 --> 00:01:57,040
+code, in a much more intuitive way, because I can see
+
+40
+00:01:57,040 --> 00:02:00,650
+right away where the control flows, while I execute the code.
+
+41
+00:02:00,650 --> 00:02:01,730
+So we're going to use this
+
+42
+00:02:01,730 --> 00:02:04,430
+representation to introduce further coverage criteria.