title: Rspec validate uniqueness with scope
body: <p>I have this in my Line model</p>
  
  <pre><code>validates :home_team, :uniqueness =&gt; { :scope =&gt; [:visiting_team, :event_datetime],
  :message =&gt; "** DOUBLE EVENT **" }  
  </code></pre>
  
  <p>I have this in my spec</p>
  
  <pre><code>describe Line do
    it { should validate_uniqueness_of(:home_team).scoped_to(:visiting_team, :event_datetime) }  
  </code></pre>
  
  <p>I get this error...</p>
  
  <p>Failures:</p>
  
  <pre><code>1) Line 
   Failure/Error: 
  
  it { should validate_uniqueness_of(:home_team).scoped_to(:visiting_team, :event_datetime) }
     Did not expect errors to include "has already been taken" when home_team is set to "arbitrary_string", got error: 
  # ./spec/models/line_spec.rb:7:in `block (2 levels) in &lt;top (required)&gt;'
  </code></pre>
  
  <p>Any ideas why this is failing?</p>