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In this case we focus on white box testing. So consider now this

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other function, called fun. And let's assume that we want to test this function

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without having a specification. So without knowing exactly what it needs to do.

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But just by looking at the code. So we will try to do the

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problem in this case is to try to just execute all the statements.

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In the function. And notice I will talk extensively of what does it

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means to do white box testing later on in the next, two classes.

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So if that's our goal, if our goal is to cover all the statements,

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any input will really do. So any test case

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will excecute all statements in the code. And we'll a

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complete, you know, white-box testing coverage for the program.

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Imagine that I now give you a specification for this

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function. And what the specification says is that this

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function inputs an integer parameter, param, and returns half of

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its value, if param is even, and its value

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unchanged otherwise. That means if param is odd. So looking

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at this specification, we can clearly see that the function fun

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works correctly only for even integers, and it doesn't work for

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odd integers. Because it computes. Half of the value of the

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parameter and returns it every time, no matter what param is. So

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this is a case in which white box testing could easily

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miss the problem, because as we said any input will exercise

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the code. It's just by chance that we could reveal one

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that revealed the problem in the code. Conversely if we were to

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work, in a black box manner. Typically looking at the specification, we

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will select at least one odd, and one even input number to

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exercise all of the specified behavior. And we will find the problem

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right away. So these two examples are just very small examples, and

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they're kind of, you know, stretched. But these kind of issues occur

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on a much bigger scale and in much more subtle ways in

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real world software. And so what this examples do is to show

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you, how black box and white box tests are really complimentary techniques.

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So in the next two lessions we will explore

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these two types of techniques in detail. We will

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see different kinds of white box and black box

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testing. And we'll talk about their strengths and the mutations