How do I test Rails block helpers with rSpec

<% some_block_helper do %>
  Some arbitrary HTML and ERB variables here.
  More HTML here.
<% end %>

describe SomeHelper do
  it 'should do something' do
    helper.some_block_helper { the_block_code }.should XXXX
  end
end

describe SomeHelper do
  it 'should do something' do
    content = lambda { "blah" }
    result  = helper.some_block_helper(&content)

    result.should include("blah")
    result.should XXX
  end
end