testing revisited - outside-in

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Testing Revisited: Driving Implementation with Outside-in Specs Thursday, June 21, 12

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Testing isn’t about veriﬁcation, per se Thursday, June 21, 12

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It’s a design tool Thursday, June 21, 12

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An outline Thursday, June 21, 12

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Executable system speciﬁcation Thursday, June 21, 12

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Red Green Refactor Thursday, June 21, 12

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1) Write a spec Thursday, June 21, 12

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1) Write a spec See it fail Thursday, June 21, 12

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2) Write enough code to make it pass Thursday, June 21, 12

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2) Write enough code to make it pass Make it green Thursday, June 21, 12

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3) Refactor the implementation and/or specs Thursday, June 21, 12

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3) Refactor the implementation and/or specs Clean the code, reduce duplication Thursday, June 21, 12

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http://jakegoulding.com/blog/2011/10/10/learned-about-testing-last-year/ Thursday, June 21, 12

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1) Write an acceptance test Thursday, June 21, 12

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1a) Write a spec Thursday, June 21, 12

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1b) Write enough code to make it pass Thursday, June 21, 12

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1c) Refactor the implementation and/or specs Thursday, June 21, 12

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2) Write enough unit tests and code to pass the acceptance test Thursday, June 21, 12

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3) Refactor Thursday, June 21, 12

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4) Repeat Thursday, June 21, 12

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Sometimes, we want to isolate the item under test from another dependency Thursday, June 21, 12

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A dependency is any external piece of code the item under test relies on or collaborates with Thursday, June 21, 12

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When a dependency is expensive or difﬁcult to use, it may be a good idea to swap it out for a test double Thursday, June 21, 12

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Test doubles: stubs and mocks Thursday, June 21, 12

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stub: a “dumb” stand-in for a real object that responds to messages (methods), sometimes returning canned responses Thursday, June 21, 12

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Used when we want to isolate the code under test from uncertainty or costly execution Thursday, June 21, 12

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mock: a stand-in for a real object that expects to receive messages (methods) and provides testing veriﬁcation Thursday, June 21, 12

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Used when we want to test (verify) that the code under test collaborates properly with its depedencies Thursday, June 21, 12

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Random thoughts Thursday, June 21, 12

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Testing is hard - especially BDD/TDD Thursday, June 21, 12

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Well, it’s easy. It’s just subtle. Thursday, June 21, 12

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Practice, practice, practice. Thursday, June 21, 12

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People do it “wrong”. Often. Thursday, June 21, 12

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They will think they’re doing it right. Or at least, doing it less wrong than they are. Thursday, June 21, 12

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Testing is a religion - especially TDD/BDD Thursday, June 21, 12

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Testing is a religion - especially TDD/BDD People will evangelize. Thursday, June 21, 12

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Testing is a religion - especially TDD/BDD People will evangelize. And they’re wrong. Thursday, June 21, 12

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Read. Learn. Practice, practice, practice. Thursday, June 21, 12

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Example: Add refeeds to simple_feed Include “refeeded” count Thursday, June 21, 12

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Exercise: Add show/hide item to simple_feed Add a link on items the user owns to hide them, or to show them for hidden items. Thursday, June 21, 12