The difference between RSpec, Capybara and Cucumber

by Jason Swett,

If you’re new to Rails testing you’ve probably come across the terms RSpec, Capybara and Cucumber.

All three are testing tools. What are they for? Do you need all of them? Here are some answers.

RSpec

RSpec is a testing framework. It’s what allows you to write and run your tests.

An analogous tool would be MiniTest. In my experience, most commercial Rails projects use RSpec and most open-source Ruby projects use MiniTest. At any Rails job you’re more likely to be using RSpec than MiniTest. (I’m not sure why this is the way it is.)

Capybara

Some Rails tests operate at a “low level”, meaning no browser interaction is involved. Other “high level” tests do actually spin up a browser and click links, fill out form fields, etc.

Low-level tests can be executed with just RSpec and nothing more. But for tests that use the browser, something more is needed.

This is where Capybara comes into the picture. Capybara provides helper methods like fill_in to fill in a form field, click_on to click a button, etc.

Please note that Capybara does NOT have to be used in conjunction with Cucumber. It’s completely possible to write integration tests in Rails with just RSpec and Capybara.

Cucumber

Cucumber is a tool for writing test cases in something close to English. Here’s an example from Wikipedia:

Cucumber can be connected with RSpec and Capybara and used to write integration tests.

My personal take on Cucumber is that while the English-like syntax might appear clearer at first glance, it’s actually less clear than bare RSpec/Capybara syntax. (Would a Ruby class be more understandable if it were English instead of Ruby?)

Cucumber adds both a layer of mental overhead and a layer of maintenance overhead on top of the RSpec + Capybara combination. I always try as hard as I can to try to steer new testers away from Cucumber.

“So, what should I use to test my Rails apps?”

My advice is to use the combination of RSpec + Capybara and forget about Cucumber. What if you don’t know where to start with writing RSpec/Capybara tests? If that’s the case, you might like to check out my guide to RSpec + Capybara testing, which includes a tutorial.

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One thought on “The difference between RSpec, Capybara and Cucumber

  1. Brian Loomis

    I would agree with the comments about cucumber to the point that if you can really help get stakeholders or product owners involved in writing use cases that explaining the Gerkin syntax to them in a few minutes is doable, and they can actually write good declarations.
    The tradeoff is that writing features in cucumber means that you also write step definitions and those are typically outside of regular tests you may be writing for the app. Cucumber however can be used to do testing without Capybara, which just means making the step definitions do different things that automating the browser.

    Reply

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