Selecting a radio button with Rspec

I'm currently writing a test for a form using RSpec, and I was wondering how I'd go about selecting a radio button, given the form below:

<%=form_for(@whatever) do|f|%>

         <%=f.label :option, "TRUE" %>
         <%=f.radio_button :option, true %>
         <%=f.label :option, "FALSE" %>
         <%=f.radio_button :morning, false %>

         <%=f.submit "SAVE" %>
      <% end %>

I want my test to look something like:

       describe "with valid options selected" do

          before do
            #CODE TO SELECT A RADIO BUTTON
            click_button "SAVE"
          end

        end