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139 lines
5.9 KiB
139 lines
5.9 KiB
11 months ago
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<title>Julio Biason .Me 4.3</title>
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<link rel="stylesheet" href="https://blog.juliobiason.me/print.css" media="print">
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<div class="container sidebar-sticky">
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<div class="sidebar-about">
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<a href="https://blog.juliobiason.me"><h1>Julio Biason .Me 4.3</h1></a>
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<p class="lead">Old school dev living in a 2.0 dev world</p>
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</div>
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<li class="sidebar-nav-item"><a href="/">English</a></li>
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<li class="sidebar-nav-item"><a href="/pt">Português</a></li>
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<li class="sidebar-nav-item"><a href="/tags">Tags (EN)</a></li>
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<li class="sidebar-nav-item"><a href="/pt/tags">Tags (PT)</a></li>
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</ul>
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<div class="content container">
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<div class="post">
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<h1 class="post-title">Things I Learnt The Hard Way - Testing Every Function Creates Dead Code</h1>
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<span class="post-date">
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2019-06-21
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<a href="https://blog.juliobiason.me/tags/books/">#books</a>
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<a href="https://blog.juliobiason.me/tags/things-i-learnt/">#things i learnt</a>
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<a href="https://blog.juliobiason.me/tags/unit-tests/">#unit tests</a>
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<a href="https://blog.juliobiason.me/tags/dead-code/">#dead code</a>
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</span>
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<p>If you write a test for every single function on your system, and your system
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keeps changing, how will you know when a function is not necessary anymore?</p>
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<span id="continue-reading"></span>
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<p>Writing a test for every single function on your system may come from the
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"100% Coverage Syndrome", which afflicts some managers, thinking that the only
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way to be completely sure your system is "bug free" is to write tests for
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every single line of code, till you reach the magical "100% coverage" in all
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the tests.</p>
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<p>I do believe you can reach 100% coverage, as long as you're willing to
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<em>delete</em> your code.</p>
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<p>(Cue the universal grasps here.)</p>
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<p>But how do you know which pieces of code can be deleted?</p>
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<p>When I mentioned <a href="/books/things-i-learnt/integration-tests">integration
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tests</a>, I mentioned how much more
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sense it made to me reading them instead of the "unit" tests, because they
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were describing exactly how the system would operate in normal (and some
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abnormal) conditions. If you write tests that go through the system, assuming
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it is a black box with an input point and an output, and you can get tests for
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all the normal cases -- and some "abnormal", like when things go wrong -- then
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you know that, if you run those tests and they mark some lines as "not
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tested", it's because you don't need them.</p>
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<p>"But Julio, you're forgetting the error control!" I do agree, specially when
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you're talking with project owners or some other expert, that people will
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forget to tell you what to do in case of things going wrong -- say, the user
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typing their name in the age field -- but <em>you</em> can see those and <em>you</em> know
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that you need error control so <em>you</em> can add the error control and describe
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the situation where that error control would trigger.</p>
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<p>If, on the other hand, you write a test for every function, when you do a
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short/simple check, you'll find that the function is still being used in the
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system by the tests, not actually, "value to the user" code. Sure, you can
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use your IDE to go back and forth between code and test and see if it points a
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use beyond the test, but it won't do it for yourself.</p>
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<p>There is one other weird thing about using integration tests for error
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controls: Sometimes, you can't reach the control statement. It's true! I did
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wrote control checks for every function once but, when running in the
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integration tests, there was no way to produce an input at the input layer of
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the system that would reach the error control in that function 'cause the
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other functions, which would run before the one I was trying to test, would
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catch the error before it. If that's a design problem or not -- it probably
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was -- it's a different discussion, but the fact is that that function didn't
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need error control, something that I wouldn't see if I wrote test specifically
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for it, but it was clear in an integration test run.</p>
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<div>
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<div style="float:left">
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<< <a href="/books/things-i-learnt/integration-tests">Unit Tests Are Good, Integration Tests Are Gooder</a>
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</div>
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<div style="float:right">
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<a href="/books/things-i-learnt/tests-apis">Tests Make Better APIs</a> >>
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</div>
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</div>
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