I’m working on the RubyLearning blog’s Ruby Programming Challenge for Newbies #1 to learn the language – I’ve done a bit with Rails and some admin scripts so I could use the exposure.  Since I love TDD approaching Ruby development through RSpec is only natural, but it was a pain in the ass trying to find how I could have RSpec verify that my program properly exited when certain conditions were met.  Here’s how I solved it, reposted here:

# something.rb 

class Something 

    def initialize(kernel=Kernel)
        @kernel = kernel
    end


def process_arguments(args)
    @kernel.exit
end


end

something_spec.rb

require 'something' 

describe Something do 

    before :each do
        @mockkernel = mock(Kernel)
        @mockkernel.stub!(:exit)
    end

it "should exit cleanly" do
    s = Something.new(@mock_kernel)
    @mock_kernel.should_receive(:exit)
    s.process_arguments(["-h"])
end


end

What I learned was that you can define a constructor with optional arguments (in this case, initialize(kernel=Kernel) and then proceed to use @kernel’s methods instead of the methods that Kernel provides when you do not specify a class instance.  With a properly mocked and stubbed exit method in my spec things operate as expected.