title: FluentValidation RuleForEach not detecting error?
body: <p>i have a rule defined below where the PreferredAirlineCodes is a string[] type</p>
  
  <pre><code>RuleForEach(x =&gt; x.PreferredAirlineCodes).Length(2);
  </code></pre>
  
  <p>however when I ran the following test...</p>
  
  <pre><code>validator.ShouldHaveValidationErrorFor(x =&gt; x.PreferredAirlineCodes, new []{"CX", "3KK"});
  </code></pre>
  
  <p>the test failed... did i defined the rule wrongly?</p>