RSpec fundamentals: setup, naming and basic structure
When you start programming, it’s not easy to know what to test, how to test, and why should you test? You’ve probably heard that TDD (as in Test Driven Development) is THE best practice. But at first, it’s hard to know what your code should do before you’re writing it.
Testing requires practice to reveal its potential.
When I started programming, I’d copy other people’s tests because, well, I had to test, right? But after a while, my tests would uncover edge cases, potential bugs I’d overlooked.
So, I feel a series of RSpec fundamentals - short know-hows, know-whats and, know-whys - could be of some use to newcomers. Brief essays explaining one aspect of testing with RSpec.
If this sounds fun to you, let’s start with the basics.
What is RSpec?
First, let’s begin with the obvious question: what is RSpec?
RSpec is a testing framework built in Ruby to test Ruby code. It focuses on testing the behavior of your program: what am I feeding my code? What do I expect to come out?
It’s one of several testing frameworks available out there. You might also know Minitest.
Adding RSpec to your application
The RSpec team maintains a gem, making it easy to use the framework in Rails applications.
First, add RSpec to your Gemfile.
Install the gem.
Scaffold RSpec’s configuration and switch your application’s testing framework to RSpec.
Now, run your migrations and prepare your test database.
There! Now, you can run your tests by typing
rspec spec in your shell.
spec is the folder where you’ll create your test files.
Naming your RSpec files
RSpec naming convention is straightforward:
users_controller.rbis tested by
user.rbis tested by
user_notification_job.rbis tested by
Architecturing your spec folder
To make sure RSpec and Rails work smoothly together, mimick the structure of your `app` folder.
app/models/user.rbis tested by
app/serializers/admin/book_serializer.rbis tested by
- and so on.
There’s only one catch:
app/controllers/users_controller.rbis tested by
spec/requests/users_controller.rb. The RSpec team discourages you to use
spec/controllers. Why? Because testing requests allows you to test the behaviour of your controller’s actions through the stack (routing, request, response, etc…) versus testing the controller in isolation 1.
So for testing controllers, your folder’s structure is:
The structure of your RSpec files
Let’s say we want to test our
User model. Our file’s structure would look like this:
There! Your setup is done.
But now, I’d like us to dig into each element so we get a better understanding of what’s going on.
require 'rails_helper'loads the configuration for RSpec.
rails_helper.rbis located at the root of the
specfolder. RSpec is configured out of the box so no need to worry about it.
RSpecis the core module for all RSpec code. It encapsulates and loads a lot of things on instantiation: configuration, expectations, examples, etc. You can check out the code here.
.describeis a class method defined on the
RSpecmodule. It groups your tests around a common abstraction: a class, a request, etc. In the example above, our abstraction is the
The code below is from the RSpec repository.
It’s a bit hard to read because of the metaprogramming bits, but the main idea is that it defines the
.describe instance method in the
RSpec::Core::ExampleGroup class with the abstraction you’re testing (
User) and the tests you wrote as arguments.
Useris the class you’re testing. It’s passed as an argument to the
do ... endis the block where you’re writing your tests. These will be passed as a second argument to the
I hope these explanations will give you a better understanding of how RSpec works. Next time, we’ll write our first tests.
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