Make the Invisible More Visible

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Many aspects of invisibility are rightly lauded as software principles to uphold. Our terminology is rich in invisibility metaphors; mechanism transparency and information hiding to name but two. Software and the process of developing it is, to paraphrase Douglas Adams, "mostly invisible".

  • Source code has no innate presence and doesn't obey the laws of physics. It's visible when loaded into an editor, but close the editor and it's gone. Think about it too long and like the tree falling down with no one to hear it you start to wonder if it exists at all!
  • Most source code has no visual appearance in the final running product whatsoever. Either in quantity or quality. The goings on behind Google's home page, we can be sure, are substantial, and certainly not in proportion to the number of pixels its pleasingly minimal home page lights up.

But beware. Invisibility is dangerous. We find it easier to manage things when we can see them. We generally think better when we have something concrete to hang our thoughts on. All useful practices have a core technical purpose, but the really useful ones also help to make the invisible more visible. They give confidence that progress is based on genuine evidence

  • Unit testing. Writing unit tests provides evidence about how easy the code unit is to unit test. It often helps to reveal the absence of qualities we'd like the code to exhibit; qualities such as low coupling and high cohesion. Running unit tests provides evidence about the code's behaviour. It helps to reveal the absence of qualities we'd like the application to exhibit; qualities such as robustness and correctness.

Faith is belief without evidence. I don't recommend faith based development. It's better to develop software with plenty of visible evidence.


By Jon Jagger

This work is licensed under a Creative Commons Attribution 3

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