Add additional RemexDriver paragraph-wrapper test

* This test comes from the Parsoid repository where it covers
  more code paths and specs more expectations.

Change-Id: I2c6c861e10c83808a39979659cef02fc8d42e24c

tests/phpunit/unit/includes/tidy/RemexDriverTest.php

@@ -158,6 +158,11 @@ class RemexDriverTest extends MediaWikiUnitTestCase {
 			'a',
 			'<p>a</p>'
 		],
+		[
+			'<span> is not a splittable tag',
+			'<span>x<div>a</div>y</span> <span>x<div></div>y</span>',
+			'<span>x<div>a</div>y</span> <span>x<div></div>y</span>',
+		],
 		[
 			'<span> is not a splittable tag, but gets p-wrapped in simple wrapping scenarios',
 			'<span>a</span>',