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diff --git a/usth/ICT2.7/P4L3 White-Box Testing Subtitles/12 - Branch Coverage - lang_en_vs3.srt b/usth/ICT2.7/P4L3 White-Box Testing Subtitles/12 - Branch Coverage - lang_en_vs3.srt deleted file mode 100644 index a1dedad..0000000 --- a/usth/ICT2.7/P4L3 White-Box Testing Subtitles/12 - Branch Coverage - lang_en_vs3.srt +++ /dev/null @@ -1,267 +0,0 @@ -1 -00:00:00,400 --> 00:00:03,780 -So now that we know what the CFG is, let's see how we can get into a count, - -2 -00:00:03,780 --> 00:00:07,860 -that else part, that is missing in our example code by introducing a new - -3 -00:00:07,860 --> 00:00:10,480 -kind of coverage. Branch coverage. As usual, - -4 -00:00:10,480 --> 00:00:13,550 -I'm going to describe branch coverage in terms of test requirements and - -5 -00:00:13,550 --> 00:00:17,100 -coverage measure. So starting from test requirements. The test requirement for - -6 -00:00:17,100 --> 00:00:21,080 -branch coverage are the branches in the program. In other words, - -7 -00:00:21,080 --> 00:00:25,240 -the goal of branch coverage is to execute all of the branches in the program. - -8 -00:00:25,240 --> 00:00:28,370 -The coverage measure is defined accordingly as the number of branches - -9 -00:00:28,370 --> 00:00:33,150 -executed by my test cases over the total number of branches in the program. And - -10 -00:00:33,150 --> 00:00:37,020 -let me remind you that branches are the outgoing edges from a decision point. - -11 -00:00:37,020 --> 00:00:40,410 -Therefore, an if statement, a switch statement, a while statement. - -12 -00:00:40,410 --> 00:00:44,400 -Any note in the c of g that has got more than one outgoing edge. - -13 -00:00:44,400 --> 00:00:48,170 -Those edges are called branches. So let's look at that using our example. So - -14 -00:00:48,170 --> 00:00:51,690 -now we're looking back at our printSum example. And in addition to the code, - -15 -00:00:51,690 --> 00:00:54,440 -I also want to represent the CFG for the program. So - -16 -00:00:54,440 --> 00:00:58,590 -let's start by looking at how many branches we have in our code. Which means how - -17 -00:00:58,590 --> 00:01:02,070 -many test requirements we have. And in this case there are two decision points. - -18 -00:01:02,070 --> 00:01:04,940 -The first one that corresponds to the first if, and the second one that - -19 -00:01:04,940 --> 00:01:10,100 -corresponds to the second if. So we have one, two, three, and four branches. So - -20 -00:01:10,100 --> 00:01:13,880 -now, let's bring back our current set of test cases. We had two test cases. - -21 -00:01:13,880 --> 00:01:17,440 -The one's that, with which we achieved a 100% statement coverage. And - -22 -00:01:17,440 --> 00:01:21,140 -let's see what happens in terms of branch coverage when we run these test cases. - -23 -00:01:21,140 --> 00:01:24,110 -I start from the first one, when we execute it, we follow the code, - -24 -00:01:24,110 --> 00:01:27,890 -we get to this decision point because the predicate in the if statement is true. - -25 -00:01:27,890 --> 00:01:30,770 -We follow the true branch, therefore we get here and then, - -26 -00:01:30,770 --> 00:01:34,970 -we exit from the program. So, in this case, we covered one of the branches, - -27 -00:01:34,970 --> 00:01:40,710 -which means that we got to 25% coverage. Now when we run the second test case, - -28 -00:01:40,710 --> 00:01:44,160 -again we follow this path. We get to this, the first if and - -29 -00:01:44,160 --> 00:01:47,730 -in this case the predicate of the if is false. Therefore, we go this way. - -30 -00:01:47,730 --> 00:01:51,160 -We reach the second predicate, the second if. The result is true, so - -31 -00:01:51,160 --> 00:01:55,490 -we follow the true branch and therefore, we cover these additional two branches. - -32 -00:01:55,490 --> 00:01:59,900 -So at this point, we are at 75% branch coverage. So what - -33 -00:01:59,900 --> 00:02:04,070 -happens is that we're missing this branch. For now, the inputs that we consider, - -34 -00:02:04,070 --> 00:02:07,740 -this branch is executed. Therefore, we need to add an additional test case. And - -35 -00:02:07,740 --> 00:02:11,600 -that this case that we need, is one for which this predicate is false and this - -36 -00:02:11,600 --> 00:02:15,680 -predicate is false. The simplest possibility in this case is the test case for - -37 -00:02:15,680 --> 00:02:20,170 -which A is equal to 0 and B is equal to 0. If we execute this test case, - -38 -00:02:20,170 --> 00:02:24,250 -our execution again followed this path, follows the fourth branch here. - -39 -00:02:24,250 --> 00:02:28,090 -And in this case, because result is not less than zero either, will follow - -40 -00:02:28,090 --> 00:02:33,090 -this branch as well. And therefore, we will reach our 100% branch coverage. And - -41 -00:02:33,090 --> 00:02:35,820 -this covered the problem. Something that I would like to clarify before we - -42 -00:02:35,820 --> 00:02:40,920 -move to the next topic, is that 100% coverage does not provide any guarantee of - -43 -00:02:40,920 --> 00:02:44,530 -finding the problems in the code. All we saw so far is the fact that by - -44 -00:02:44,530 --> 00:02:48,580 -testing more thoroughly we have more chances of finding a problem in the code. - -45 -00:02:48,580 --> 00:02:51,680 -But it doesn't matter which kind of coverage we utilize, and how much - -46 -00:02:51,680 --> 00:02:55,440 -coverage we achieve. There's always a chance that we might miss something. And - -47 -00:02:55,440 --> 00:02:59,760 -I will get back to this later on in the lesson. I just mentioned the fact that - -48 -00:02:59,760 --> 00:03:03,910 -we tested more fully when we went from statement coverage to branch coverage. - -49 -00:03:03,910 --> 00:03:06,900 -What does that mean exactly? To explain that, I'm going to introduce the concept - -50 -00:03:06,900 --> 00:03:11,420 -of test criteria subsumption. One test criteria subsumes another criteria when - -51 -00:03:11,420 --> 00:03:16,760 -all the tests widths that satisfy that criteria will also satisfy the other one. - -52 -00:03:16,760 --> 00:03:18,740 -So let me show you that with statement and - -53 -00:03:18,740 --> 00:03:23,220 -branch coverage. If we identify a test width that achieves 100% branch coverage, - -54 -00:03:23,220 --> 00:03:27,780 -the same test width will also achieve, necessarily, 100% statement coverage. - -55 -00:03:27,780 --> 00:03:31,290 -That's what happened for our example, and also what happens in general, - -56 -00:03:31,290 --> 00:03:35,660 -because branch coverage is a stronger criteria than statement coverage. - -57 -00:03:35,660 --> 00:03:39,670 -There is no way to cover all the branches without covering all the statements. - -58 -00:03:39,670 --> 00:03:43,480 -It is not true that any test results satisfies statement coverage will also - -59 -00:03:43,480 --> 00:03:47,040 -satisfy branch coverage. And, in fact, we just saw a counter example. - -60 -00:03:47,040 --> 00:03:50,569 -When we look at the printSum code. We had a test where there was achieving 100% - -61 -00:03:50,569 --> 00:03:53,910 -statement coverage and was not achieving 100% branch coverage. Therefore, - -62 -00:03:53,910 --> 00:03:58,301 -in this case we have a substantial relation in this direction. Branch coverage, - -63 -00:03:58,301 --> 00:04:02,860 -subsumes statement coverage. What it also means is that normally, or in general, - -64 -00:04:02,860 --> 00:04:06,910 -it is more expensive to achieve branch coverage than achieve statement coverage, - -65 -00:04:06,910 --> 00:04:09,490 -because achieving branch coverage requires the generation of - -66 -00:04:09,490 --> 00:04:13,770 -a larger number of test cases. So what this relation means is that - -67 -00:04:13,770 --> 00:04:17,779 -branch coverage is stronger than statement coverage but also more expensive. |