retro testing (devcontlv jan 2014)

1Allon Mureinik - Retro Testing

Retro Testing

Allon MureinikTeam Lead, Cloud Storage, Red [email protected] / @mureinik

January 2014

mailto:[email protected]


TDD Is Easy...


... or is it?

● The first two part should be● Write a test● Make sure it fails

● The question is why it fails.

● In a legacy system, it will often fail for “bad” reasons:● Unable to access the database● Some static resource not set up● Need to spin up an application server● Etc., etc., etc...


Will the mistakes of the past haunt me forever?


It’s not an all-or-nothing situation


One baby step at a time


Refactor, refactor, refactor

● Your first task would probably be to do some refactoring

● Resist the urge to improve the code● Frankly, this step may make the code look worse

● Your only goal here is to create an opportunity to write tests


Refacroting with no tests is like...


Example : Bad Code


Some minimal refactoring


Now we can start writing tests...

● Now we have the tools to separate external resources from logic

● There are a couple of ways to do so:● Override the relevant methods in your test● Use Mockito/EasyMock to spy the tested object● Use @Rules to set up common mocking once


I @Spy With My Little Eye


Some more refactoring


Let’s modernize our code


But how can I write asserts?

● Overriding, mocking and all that jazz are fine and well

● But any test boils down to writing an assert...

● ... and I have no idea what this function is supposed to do

● Remember this is a legacy system

● You may not need to test it for correctness ...

● Just for backwards compatibility


The real challenge is changing mindset

● We can discusses refactoring till we’re blue in the face

● But the real challenge isn’t changing the way we code

● It’s changing the way we approach the problem


It’s all too easy to slip back to bad habits

● This bug is blocking the release...

● It’s a ton of work to refactor this logic out...

● The rest of the code is bad anyway...


Have the courage to stand up to excuses


Questions?

retro testing (devcontlv jan 2014)

Technology