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Retro Testing
Allon Mureinik
Team Lead, Cloud Storage, Red Hat
amureini@redhat.com / @mureinik
January 2014
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TDD Is Easy...
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... or is it?
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The first two part should be
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Write a test
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Make sure it fails
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The question is why it fails.
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In a legacy system, it will often fail for “bad” reasons:
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Unable to access the database
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Some static resource not set up
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Need to spin up an application server
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Etc., etc., etc...
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Will the mistakes of the past haunt me
forever?
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It’s not an all-or-nothing situation
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One baby step at a time
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Refactor, refactor, refactor
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Your first task would probably be to do some
refactoring
Resist the urge to improve the code
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Frankly, this step may make the code look worse
Your only goal here is to create an opportunity to write
tests
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Refacroting with no tests is like...
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Example : Bad Code
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Some minimal refactoring
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Now we can start writing tests...
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Now we have the tools to separate external resources
from logic
There are a couple of ways to do so:
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Override the relevant methods in your test
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Use Mockito/EasyMock to spy the tested object
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Use @Rules to set up common mocking once
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I @Spy With My Little Eye
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Some more refactoring
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Let’s modernize our code
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But how can I write asserts?
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Overriding, mocking and all that jazz are fine and well
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But any test boils down to writing an assert...
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... and I have no idea what this function is supposed to
do
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Remember this is a legacy system
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You may not need to test it for correctness ...
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Just for backwards compatibility
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The real challenge is changing mindset
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We can discusses refactoring till we’re blue in the face
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But the real challenge isn’t changing the way we code
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It’s changing the way we approach the problem
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It’s all too easy to slip back to bad habits
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This bug is blocking the release...
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It’s a ton of work to refactor this logic out...
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The rest of the code is bad anyway...
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Have the courage to stand up to excuses
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Questions?
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