Bug 1537760 [wpt PR 15871] - HTML: mutating the style element, a=testonly

Automatic update from web-platform-tests
HTML: mutating the style element

For whatwg/dom#800.
--

wpt-commits: 7b63b60158ca7d636aafc099079b2b1b77cdc76a
wpt-pr: 15871

Author: annevk

testing/web-platform/tests/html/semantics/document-metadata/the-style-element/mutations.window.js

@@ -0,0 +1,39 @@
+test(t => {
+  const style = document.body.appendChild(document.createElement("style"));
+  const sheet = style.sheet;
+  t.add_cleanup(() => style.remove());
+  assert_not_equals(sheet, null);
+  style.appendChild(new Comment());
+  assert_not_equals(sheet, style.sheet);
+}, "Mutating the style element: inserting a Comment node");
+
+test(t => {
+  const style = document.body.appendChild(document.createElement("style"));
+  t.add_cleanup(() => style.remove());
+  const comment = style.appendChild(new Comment());
+  const sheet = style.sheet;
+  comment.appendData("x");
+  assert_not_equals(sheet, style.sheet);
+}, "Mutating the style element: mutating a Comment node");
+
+test(t => {
+  const style = document.body.appendChild(document.createElement("style"));
+  t.add_cleanup(() => style.remove());
+  const text1 = style.appendChild(new Text("1"));
+  const text2 = style.appendChild(new Text("2"));
+  assert_equals(style.textContent, "12");
+  assert_equals(style.childNodes.length, 2);
+  const sheet = style.sheet;
+  style.normalize();
+  assert_equals(style.childNodes.length, 1);
+  assert_not_equals(sheet, style.sheet);
+}, "Mutating the style element: using normalize()");
+
+test(t => {
+  const style = document.body.appendChild(document.createElement("style"));
+  t.add_cleanup(() => style.remove());
+  const comment = style.appendChild(new Comment());
+  const sheet = style.sheet;
+  comment.remove();
+  assert_not_equals(sheet, style.sheet);
+}, "Mutating the style element: removing a Comment node");