Add LISTING tests

Author: sirreal

tests/phpunit/tests/html-api/wpHtmlProcessor-serialize.php

@@ -354,6 +354,22 @@ public static function data_provider_normalize_special_leading_newline_cases() {
 				"<pre>\n\nline 2<!--comment--> still line 2</pre>",
 				"<pre>\n\nline 2<!--comment--> still line 2</pre>",
 			),
+			'Leading newline in LISTING'             => array(
+				"<listing>\nline 1\nline 2</listing>",
+				"<listing>line 1\nline 2</listing>",
+			),
+			'Double leading newline in LISTING'      => array(
+				"<listing>\n\nline 2\nline 3</listing>",
+				"<listing>\n\nline 2\nline 3</listing>",
+			),
+			'Multiple text nodes inside LISTING'     => array(
+				"<listing>\nline 1<!--comment--> still line 1</listing>",
+				'<listing>line 1<!--comment--> still line 1</listing>',
+			),
+			'Multiple text nodes inside LISTING with leading newlines' => array(
+				"<listing>\n\nline 2<!--comment--> still line 2</listing>",
+				"<listing>\n\nline 2<!--comment--> still line 2</listing>",
+			),
 			'Leading newline in TEXTAREA'        => array(
 				"<textarea>\nline 1\nline 2</textarea>",
 				"<textarea>line 1\nline 2</textarea>",