Stub (mock) in RSpec 3


Recently, I have been doing whole bunch of spec rewriting from RSpec 2 to Rspec 3. As a result I have found that documentation is not that straightforward, and some cases you need to really spend time and figure out yourself. So I’ll be posting some cases that I have not been able to find in docs, just as notes for myself, and hopefully it will be useful for someone else.


Use Case:

I have JSON file that I need to read, and I already have tests that this JSON file opens properly.  I also have a Validator that looks for certain patterns keys in this JSON file. Validator leaves separately from the main app, and I don’t want to replicate File Upload -> File Save to Cloud -> File Open in my Validator Tests, I just want on every to return certain data, and it does not matter to me what exactly is being read, and if path exists or not.

How would I do it in Rspec ?

data = {:name => 'test'; , :description => 'test'}.to_json
allow(File).to receive(:read).and_return(data)

What does it give you ?

It looks for every in the scope of your spec and instead of actually reading file returns ‘data‘ every time.

Cool, huh ?



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Anatoly Spektor

IT Consultant with 6 years experience in Software Development and IT Leadership. Participated in such projects as Eclipse IDE, Big Blue Button, Toronto 2015 Panam Games.

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