src/third_party/web_platform_tests/webdriver/element_state/res/element-hidden-by-z-index.html - cobalt - Git at Google

 <!DOCTYPE html>
 <meta charset="utf-8" />
 <title>Element hidden by z-index</title>

 <style>
   * { position: relative }

   #overlay,
   #hidden {
     height: 50px;
     width: 50px;
   }

   #overlay {
     background: blue;

     z-index: 1;
   }

   #hidden {
     background: red;
     top: -50px;

     z-index: -1;
   }
 </style>

 <div id="overlay"></div>
 <div id="hidden"></div>
	<!DOCTYPE html>
	<meta charset="utf-8" />
	<title>Element hidden by z-index</title>

	<style>
	* { position: relative }

	#overlay,
	#hidden {
	height: 50px;
	width: 50px;
	}

	#overlay {
	background: blue;

	z-index: 1;
	}

	#hidden {
	background: red;
	top: -50px;

	z-index: -1;
	}
	</style>

	<div id="overlay"></div>
	<div id="hidden"></div>