title: Testing the content of a flash message: `The assertion was not run because of an invalid css selector`
body: <p>I would like to test whether a flash message contains certain text. So I have the line:</p>
  
  <pre><code>assert_select flash[:info], "Your fee is valid till"
  </code></pre>
  
  <p>This however fails with the error message:</p>
  
  <pre><code>DEPRECATION WARNING: The assertion was not run because of an invalid css selector.
  unexpected '#' after ''
  </code></pre>
  
  <p>Does anyone understand what I'm doing wrong?</p>