Beyond Red/Green/Refactor: Testing as a mindset

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This slide is intentionally blank Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Let's talk about drawing Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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How to draw Spider-Man Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Step 1 Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Step 2 Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Done! Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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That's not enough information Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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In fact, those inital steps seem pointless Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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You end up with all these unnecssary lines Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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That just need to be erased Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Maybe the person who taught you just wants to sell you erasers Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Drawing with lines and ovals Doesn't work Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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The relationship between steps is complex Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Beyond Red/Green/Refactor Testing as a Mindset Noel Rappin, Table XI Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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We've had a debate about TDD Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I learned that I have been a bad TDD advocate Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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TDD is easy! isn't it? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Red Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Green Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Refactor Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Red/Green/Refactor is a slogan not an instruction manual Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I may not have made the motivations for TDD clear Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I didn't want to scare people away from TDD Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Like Object-Oriented design, small problems don't show TDD well Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Fully implemented TDD solutions are boring to read about Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I may have diminished the value of TDD Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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There's still missing information Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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How do I know what ovals and lines to make? How do I know when each step is done? What if I want to draw Ms. Marvel instead? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Why are ovals and lines a good way to draw Spider-Man? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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How do I decide what to test next? How do I know when I'm done? What do I refactor? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Why is test-first a good way to write software? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Encourages you to think about the problem In small, focused steps In a way that reinforces specific good practices Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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What is sometimes called "outside-in" testing is a special case Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Write a test Make it pass with an incomplete implementation Write a more focused test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Broad tests that catch lots of errors Focused tests that drive design and show where the error is Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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A lot of problems seem easy to acceptance test But hard to unit test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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"What to test next" is a design question Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Given a sequence of digits 1 to 9, such as [1, 1, 2, 3, 8] 4 The sum is 15 4 At least one digit appears exactly twice 4 No digit appears more than twice 4 Order is irrelevant Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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code at https://github.com/noelrappin/spec_sequence Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Here's what might be the most obivous test: it "knows a valid sequence" do expect(Sequence.new(1, 1, 2, 3, 8)).to be_valid end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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And then we would make that test pass... Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Wait, How would we make that test pass? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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We could write the whole algorithm Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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But that is not letting the test drive the design Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Instead, let's take a small step Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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class Sequence def init(*items) @items = items end def valid? true end end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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This makes the test pass Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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This is OK Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Because it is not permanent Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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It's sometimes called "sliming the test" Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Okay, now what? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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First option: Stay at same abstraction level Write a test case that fails Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Broken code it "knows a valid sequence" do expect(Sequence.new(1, 1, 2, 3, 9)).not_to be_valid end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Normally a good option Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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In this case, though, it leads to another round of "how do we make this pass?" Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Rule of thumb: If it's not clear how you might make a test pass, there's probably a smaller test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Option 2 Go to a less abstract or smaller piece Write a failing test there Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Searching for that smaller test is where design happens Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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(Sometimes, that smaller test is not worth writing) Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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A more focused test might be: Part of the job One of the cases An error case Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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In this case: easy to target the individual clauses (sum of 15, has a pair, etc..) Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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A smaller test it "can tell if the sum is 15" do expect(Sequence.new(7, 8).to be_correct_sum) end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Why is that better? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Because it's small enough that I can write it without thinking too hard Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Like so def correct_sum? items.inject(:+) == 15 end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I don't need to slime this test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Also, I can negate it easily it "can tell if the sum is not 15" do expect(Sequence.new(7, 8, 1).not_to be_correct_sum) end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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TDD should reduce cognitive load Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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So from here, I can do 4 has a digit pair 4 does not have a digit trio 4 is unique Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Once those are in place, the not_valid test is simpler Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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A plan: Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Start with a broad test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Find a piece that can be encapsulated Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Test a happy-path solution Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Try to break it Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Where did design come in? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I design my functionality as I write the end-to-end test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I design my code structure as I break the code up Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I design my internal API as I write the happy-path test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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I refactor to keep my design clean Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Sarah Mei Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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code at https://github.com/noelrappin/spec_sequence Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap

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Noel Rappin Table XI (tablexi.com) @noelrap 4 http://www.noelrappin.com/trdd 4 http://pragprog.com/book/nrtest2/rails-4-test- prescriptions 4 http://www.patreon.com/noelrap Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap