require 'yaml'

def spit_context context, level=0
  spaces = "  " * level

  puts "#{spaces}context '#{context[0]}' do"
  puts "#{spaces}  setup do\n#{spaces}  end\n\n"
  spit_specs(context[1], level)
  puts "#{spaces}end\n\n"
end

def spit_specs speclist, level
  spaces = "  " * (level + 1)
  while spec = speclist.shift
    if spec.is_a?(Array)
      spit_context(spec, level+1)
     else
      puts "#{spaces}it '#{spec}' do"
      puts "#{spaces}end\n\n"
    end
  end
end

fname = ARGV[0] || 'spec.yml'
YAML.load(File.read(fname)).each do |context|
  spit_context(context)
end

__END__

An example file might look like

---
- - My Controller
  - - should perform some action
    - should perform some other action
    - - When used by an admin
      - - should perform another action
        - should perform yet another action