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54 lines
2.1 KiB
54 lines
2.1 KiB
4 years ago
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title = "Code is a Book, Unit Tests are Spellcheckers"
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date = 2020-02-14
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[taxonomies]
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tags = ["unit tests", "testing", "integration tests", "books", "code"]
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If we use an analogy for code as being the words in a book and the system
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being built as the whole book, then what are unit tests?
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<!-- more -->
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I just found this analogy pretty good[^1]: You can to think about your code
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as a book: Each module is a chapter, each class is a paragraph and each
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function is a sentence.
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In that analogy, were would unit tests sit?
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To me, the unit tests are like spell checkers -- or, at least, the more modern
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ones: Are you writing the proper words? Are your sentences grammatically
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correct? The spell checker will take care of this.
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But there is one thing that the spell checker won't do: make sure the chapter
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makes sense in the whole context of the book. Escaping the analogy for a
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moment, let me ask you this: Have you read "Les Misérables"? I did, and there
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is one chapter in the middle of the book in which Victor Hugo discuss the
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Battle of Waterloo. Although it makes sense in the historical point of the
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story of Les Misérables, it makes absolutely no sense in the general story
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itself -- no matter how well punctuate, correct in spelling and grammar it may
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be.
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This is a huge failure of unit tests: They don't see the whole. The whole is
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given by reviewers of a book and integration tests of a system. Jumping back
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to the analogy, when you have your integration tests defined by the system
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requisites, anything that isn't being covered is a chapter that doesn't make
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sense in the whole of the book.
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In the long run, as writers will remember the times the spell checker
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pointed a word was spelled wrong or a verb was in the wrong tense and, thus,
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make it pop less and less, so does unit tests: In the long run, the ROI[^2] of
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unit tests tend to go down, while the integration tests -- the ones that check
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if the "chapter" makes sense in the story being told by the "book" -- tend to
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go up.
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And I just found the analogy so good for the way I see those two test
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methodologies.
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---
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[^1]: ... but I lost the source of it. :(
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[^2]: "Return Of Investment"
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