ontainer div {
            position: absolute;
            height: 150px;
            width: 150px;
        }
        .container .test {
            box-shadow: red 10px 10px;
            left: 0;
            top: 0;
        }
        .container .ref {
            background-color: green;
            left: 10px;
            top: 10px;
        }
    </style>
</head>
<body>
    <p>The test passes if there is a filled green square and no red.</p>
    <div class="container">
        <div class="test"></div>
   