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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
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