title: How do I specify a failure message for assert in Rspec/Capybara
body: <p>In my rspec integration tests, when I have an assertion such as:</p>
  
  <pre><code>assert page.has_content? some_value
  </code></pre>
  
  <p>if the assertion fails, it displays:</p>
  
  <pre><code>MiniTest::Assertion: 
  Failed assertion, no message given
  </code></pre>
  
  <p>The minitest docs say "All assertion methods accept a msg which is printed if the assertion fails" but I cannot find any examples of HOW to specify the message. These are NOT valid syntax:</p>
  
  <pre><code>assert("custom fail msg") page.has_content? some_value
  
  assert page.has_content? some_value, "custom fail msg"
  </code></pre>