3_HOW_TO_TEST_CLASSES.md

How to Test Classes

Here's a sample template for how to describe a class.

spec/[type of class]/class_name_spec.rb

require "spec_helper" # Pulls in all of Rspec's goodness. The rest of your files should be auto-loaded.

describe ClassName do

  # Describe each method on your class.
  # Note that the `describe` call limits the scope of everything inside it.
  
  # This is how you describe a "class method", defined in your class like this:
  # def self.class_method
  #   ...
  # end
  # 
  # Results in a failure that looks like this:
  #
  #   ClassName.class_method failed ...
  #
  describe ".class_method" do
    # ...
  end
  
  # This is how you describe an "instance method", defined like this:
  # def instance_method
  #   ...
  # end
  #
  # Results in a failure that looks like this:
  #
  #   ClassName#instance_method failed ...
  #
  describe "#instance_method" do
    # Do setup for the method with "let" syntax. Your method is
    # going to need an instance of your class to operate on, for
    # example.
    let(:class_name) { ClassName.new }
    let(:some_var) { some_value }
    # etc...
    
    # Set the subject
    subject { class_name }
    
    # Run any additional setup you need. `before` runs before every 
    # "it" block in the current scope.
    before { do_some_more_setup }
    
    # When you're testing expectations like should_receive, 
    # you might find `after` useful.  It runs after every
    # "it" block in the current scope.
    after { call_some_method_that_should_trigger_expectations }
    
    # "it" and "its" implicitly refer to the subject
    it { should be_something }
    
    # Use "its" to test methods on the subject
    its(:attribute) { should be == some_value }

    # When you have test that needs more explanation, use a
    # wordy "it" block like so:
    it "does some complicated thing" do
      # test here
    end
    
    # Does your method do different things in different
    # scenarios?  If so, use `context`.  
    context "when some criteria is true" do
      # then actually make the criteria the case using a "let" block
      # then add your tests in that scenario
    end
    
    context "when some criteria is not true" do
      # etc
    end
    
    # NOTE: Context also limits everything inside to that context.
  end
end

How Thorough Should I Be?

Start by being very thorough. Test all the methods in your class. Once you get familiar with the toolchain and the rspec syntax, you can start easing off and only test the truly important methods.