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+So now that we know what the CFG is, let's see how we can get into a count,
+
+2
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+that else part, that is missing in our example code by introducing a new
+
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+kind of coverage. Branch coverage. As usual,
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+I'm going to describe branch coverage in terms of test requirements and
+
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+coverage measure. So starting from test requirements. The test requirement for
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+branch coverage are the branches in the program. In other words,
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+the goal of branch coverage is to execute all of the branches in the program.
+
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+The coverage measure is defined accordingly as the number of branches
+
+9
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+executed by my test cases over the total number of branches in the program. And
+
+10
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+let me remind you that branches are the outgoing edges from a decision point.
+
+11
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+Therefore, an if statement, a switch statement, a while statement.
+
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+Any note in the c of g that has got more than one outgoing edge.
+
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+Those edges are called branches. So let's look at that using our example. So
+
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+now we're looking back at our printSum example. And in addition to the code,
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+I also want to represent the CFG for the program. So
+
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+let's start by looking at how many branches we have in our code. Which means how
+
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+many test requirements we have. And in this case there are two decision points.
+
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+The first one that corresponds to the first if, and the second one that
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+corresponds to the second if. So we have one, two, three, and four branches. So
+
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+now, let's bring back our current set of test cases. We had two test cases.
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+The one's that, with which we achieved a 100% statement coverage. And
+
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+let's see what happens in terms of branch coverage when we run these test cases.
+
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+I start from the first one, when we execute it, we follow the code,
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+we get to this decision point because the predicate in the if statement is true.
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+We follow the true branch, therefore we get here and then,
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+we exit from the program. So, in this case, we covered one of the branches,
+
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+which means that we got to 25% coverage. Now when we run the second test case,
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+again we follow this path. We get to this, the first if and
+
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+in this case the predicate of the if is false. Therefore, we go this way.
+
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+We reach the second predicate, the second if. The result is true, so
+
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+we follow the true branch and therefore, we cover these additional two branches.
+
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+So at this point, we are at 75% branch coverage. So what
+
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+happens is that we're missing this branch. For now, the inputs that we consider,
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+this branch is executed. Therefore, we need to add an additional test case. And
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+that this case that we need, is one for which this predicate is false and this
+
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+predicate is false. The simplest possibility in this case is the test case for
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+which A is equal to 0 and B is equal to 0. If we execute this test case,
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+our execution again followed this path, follows the fourth branch here.
+
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+And in this case, because result is not less than zero either, will follow
+
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+this branch as well. And therefore, we will reach our 100% branch coverage. And
+
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+this covered the problem. Something that I would like to clarify before we
+
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+move to the next topic, is that 100% coverage does not provide any guarantee of
+
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+finding the problems in the code. All we saw so far is the fact that by
+
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+testing more thoroughly we have more chances of finding a problem in the code.
+
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+But it doesn't matter which kind of coverage we utilize, and how much
+
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+coverage we achieve. There's always a chance that we might miss something. And
+
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+I will get back to this later on in the lesson. I just mentioned the fact that
+
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+we tested more fully when we went from statement coverage to branch coverage.
+
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+What does that mean exactly? To explain that, I'm going to introduce the concept
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+of test criteria subsumption. One test criteria subsumes another criteria when
+
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+all the tests widths that satisfy that criteria will also satisfy the other one.
+
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+So let me show you that with statement and
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+branch coverage. If we identify a test width that achieves 100% branch coverage,
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+the same test width will also achieve, necessarily, 100% statement coverage.
+
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+That's what happened for our example, and also what happens in general,
+
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+because branch coverage is a stronger criteria than statement coverage.
+
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+There is no way to cover all the branches without covering all the statements.
+
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+It is not true that any test results satisfies statement coverage will also
+
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+satisfy branch coverage. And, in fact, we just saw a counter example.
+
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+When we look at the printSum code. We had a test where there was achieving 100%
+
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+statement coverage and was not achieving 100% branch coverage. Therefore,
+
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+in this case we have a substantial relation in this direction. Branch coverage,
+
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+subsumes statement coverage. What it also means is that normally, or in general,
+
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+it is more expensive to achieve branch coverage than achieve statement coverage,
+
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+because achieving branch coverage requires the generation of
+
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+a larger number of test cases. So what this relation means is that
+
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+branch coverage is stronger than statement coverage but also more expensive.