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Using Ruby's Eval To Make Cucumber Bigger And Greener

· · Posted in Programming
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In case you just crawled out from under your rock just to read my blog, and haven't the foggiest, cucumber is a ruby acceptance testing framework, and works great with rails.

I was writing features for admin users in this application, and needed a step like this:

Then I should be editing "test@example.com"

Where the quoted email is the login. Later on (in fact right after…I was testing edit functionality, and after safe you end up on the view user page), I had:

Then I should be viewing "test@example.com"

So I had two steps:

That's all good and fun, except they are virtually the same. Ruby has a great feature (like some other languages) call eval. You can pass it some ruby code, and it runs it in the current binding (or scope, context, whatever you want to call it. Ruby calls it binding). While using eval is sort of like goto, in that sometimes it can be dangerous, test code isn't exactly customer facing, so we can assume that test code is safe to do bad things. You wouldn't want to blindly eval user input for example.

In this case however, I could make things better:

So I have the step which is good for editing or viewing, checks the method, and makes the function name based on which method (edit_user_path or user_path), then eval that, getting the user by login. The login object is local to the block and the eval just sucks it in, since the binding ends up being the same. In short: it just works.

Behold the power of ruby!


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