fixed test

lib/single-file/serializer.js

@@ -30,7 +30,7 @@ this.serializer = this.serializer || (() => {
 		{ tagName: "head", accept: element => !element.childNodes.length || element.childNodes[0].nodeType == Node.ELEMENT_NODE },
 		{ tagName: "body", accept: element => !element.childNodes.length },
 		{ tagName: "tbody", accept: element => element.childNodes[0] && element.childNodes[0].tagName == "TR" },
-		{ tagName: "colgroup", accept: element => element.childNodes[0] && element.childNodes[0].tagName == "TR" },
+		{ tagName: "colgroup", accept: element => element.childNodes[0] && element.childNodes[0].tagName == "COL" },
 	];
 	const OMITTED_END_TAGS = [
 		{ tagName: "html", accept: next => !next || next.nodeType != Node.COMMENT_NODE },