Stop using development mode

Stop using development mode

Rails development mode is easy, useful and fast: we can spin up an app, edit its source, hit reload in a browser and see the result of our changes. But what effect does this workflow have on our code, and does it really help us? In this talk I look at the dark side of development mode — where it falls down, what it does wrong, and how it ultimately encourages us to develop software in the wrong way — and suggest an alternative way of working which avoids these disadvantages.

Given at Railsberry ( There's a video of this talk at


Tom Stuart

April 20, 2012


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    why write tests when you can press reload? the app

    works! now write tests so you don’t feel guilty the app broke! now write tests so it doesn’t break again
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    write a migration write a model write a controller write

    a template write a route press reload
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    Development mode doesn’t let you see anything working until you’ve

    completed a full vertical slice through the application.
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