gistfile1.txt

execute "create swapfile" do
  command <<-eof
    dd if=/dev/zero of=#{swap_location} bs=1M count=#{swap_size_megs} &&
    chmod 600 #{swap_location} &&
    mkswap #{swap_location}
  eof

  not_if { File.exists?("#{swap_location}") }
end

describe "create space" do
  it "turns the file into swap" do
    @chef_run.should execute_command "mkswap /var/swapfile"
  end 
end

###

Failures:

  1) swap::default create space turns the file into swap
     Failure/Error: @chef_run.should execute_command "mkswap /var/swapfile"
       expected chef_run: recipe[swap::default] to execute command "mkswap /var/swapfile"
     # ./cookbooks/swap/spec/swap_spec.rb:18:in `block (3 levels) in <top (required)>'

Finished in 0.00396 seconds
1 example, 1 failure

You could do something like:

it "turns the file into swap" do
  swap_commands = @chef_run.resources.find do |r|
    r.resource_name == :execute and r.name == 'create swapfile'
  end.command.lines.map{|c| c.strip}
  swap_commands.should include 'mkswap /var/swapfile'
end