Pushed straight to the master branch as https://github.com/ckeditor/ckeditor5-engine/pull/1812 got R+ed and this is ultra small and safe change.
@@ -465,6 +465,8 @@ describe( 'View', () => {
domSelection.collapse( newDiv, 0 );
viewDocument.fire( 'keydown', { keyCode: keyCodes.arrowright, domTarget: view.domRoots.get( 'main' ) } );
+
+ newDiv.remove();
} );