Question

I’m writing a gem that can be used both with and without rails. In a few places I use code like

path = Rails.root if defined?(::Rails)

and I want to test this logic with rspec. I have tried stubbing it like

stub(:"::Rails").should_receive(:root).and_return("/rails")

but this does not make defined?(::Rails) evaluate to true.

Answer 1

Even if defined?(::Rails) is evaluated to true, you still need a Rails object to inject the method stub. There might be several ways to do this, following is a example of my preferred approach:

before(:each) do
  unless defined?(::Rails)
    @mocked_rails_class = true
    class ::Rails
    end
  end
end

it do
  ::Rails.should_receive(:root).and_return('/rails')
  your_method.should == '/rails'
end

after(:each) do
  # Clean up the Rails class if it's generated by the test case. 
  Object.send(:remove_const, :Rails) if @mocked_rails_class
end

I’m not sure if it works on all ruby version, but at least it can work on Ruby 1.9.x.