How to use RSpec without Rails?

The process is as follows:

Install the rspec gem from the console:

gem install rspec

Then create a folder (we’ll name it root) with the following content:

root/my_model.rb

root/spec/my_model_spec.rb

#my_model.rb
class MyModel
  def the_truth
    true
  end
end

#spec/my_model_spec.rb

require_relative '../my_model'

describe MyModel do
  it "should be true" do
    MyModel.new.the_truth.should be_true
  end
end

Then in the console run

rspec spec/my_model_spec.rb

voila!