Rspec: Should be (this or that)

Question

What would be the best way to write the rspec in a situation where either of two (or more) outcomes are acceptable?

Here\'s an example of what I want to do. This is

Answer 1

Another way of writing it with the expectation on the right of the should:

it 'should be heads or tails' do
  flip_coin.should satisfy{|s| ['heads', 'tails'].include?(s)}
end