title: Is there an idiomatic way to dry up repeated method calls in RSpec
body: <p>When the same call is made repeatedly in the same describe block e.g.</p>
  
  <pre><code>RSpec.describe Grant do
    let(:grant) { Grant.make }
  
    describe "#exchange!" do
      it "destroys token" do
        grant.exchange! # dry me up!
        expect(grant).to be_destroyed
      end
      it "returns a Token" do
        expect(grant.exchange!).to be_a(Token) # dry me up!
      end
    end
  end
  </code></pre>
  
  <p>I want to dry up <code>grant.exchange!</code></p>
  
  <p>I've worked out how to do it with <code>subject</code>, but I know explicit subjects are smelly.</p>