def contains_text(expected_text)
      assert_exists
      return nil unless respond_to? :text

      case expected_text
      when Regexp
        text() =~ expected_text
      when String
        text().index(expected_text)
      else
        raise TypeError, "expected String or Regexp, got #{expected_text.inspect}:#{expected_text.class}"
      end
    end
def contains_text(expected_text)
      assert_exists
      return nil unless respond_to? :text

      case expected_text
      when Regexp
        text() =~ expected_text
      when String
        text().index(expected_text)
      else
        raise TypeError, "expected String or Regexp, got #{expected_text.inspect}:#{expected_text.class}"
      end
    end
Check if the element contains the given text.

 @param  [String, Regexp] expected_text The text to look for.
 @return [Fixnum, nil]  The index of the matched text, or nil if it doesn't match.