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Now let me conclude the lesson by summarizing a few important
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aspects of white-box testing. The first important aspect is that white-box
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testing works on a formal model. The code itself are models
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derived from the code. So when we do white-box testing, we
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don't need to make subjective decision, for example, on the level
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of obstruction of our models. Normally, we simply represent what's there.
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And so what we will obtain are objective, results and objective
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measures. As I also said at the beginning, coverage criteria allows
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us to compare different test suites, different sets of tests,
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because I can measure the coverage achieved by one test suite
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and by the other, and then decide which one to use
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based on this measure. And again, remember, these measures aren't perfect,
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but they at least give you an objective number, an objective
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measure of the likely effectiveness of your tests. So even though
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achieving 100% coverage does not mean that you identify all the
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problems in the code for sure. If your level of coverage
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is 10%, for example, for stemen coverage. That means that
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you haven't exercised 90% of your code, and therefore the trouble
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is in a piece of software that is inadequately tested
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and likely to be of inadequate quality. We also saw that
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there are two broad classes of coverage criteria, practical criteria
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that we can actually use, and theoretical criteria that are interesting
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from a conceptual standpoint, but that they are totally impractical.
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They are too expensive to be used on real world software.
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And finally, as we also said at the beginning,
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one of the great things about white box testing and
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coverage criteria, is that they are fully automatable. There are
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tools that can take your code, instrument it automatically. And
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when you run your test cases, they will tell
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you, what is the level of coverage that you achieve
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with your test at no cost for you. So there's
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really no reason not to measure coverage of your code.
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