title: Combine multiple let statements
body: <p>How can I define a method <code>create_all</code> that allows me instead of writing</p>
  
  <pre><code>describe "some spec" do
    let(:a) { create :a }
    let(:b) { create :b, :a =&gt; a }
    ...
  </code></pre>
  
  <p>to write</p>
  
  <pre><code>describe "some spec" do
    create_all
    ...
  </code></pre>
  
  <p>More specifically: <strong>Where</strong> do I have to define it in order to be able to use it in the <code>describe</code> context?</p>
  
  <p>It should work across different spec files.</p>