height: 300px;
}
.w3 {
    width: 300px;
}
.h4 {
    height: 400px;
}
.w4 {
    width: 400px;
}
.border-box, .flexbox > div {
    box-sizing: border-box;
    height: 100px;
    width: 100px;
    border: 2px solid lightblue;
    border-top-width: 4px;
    padding: 3px;
}
</style>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<script src="../../resources/check-layout-th.js"></script>
<body>
<div id=log></div>

All blue boxes are 100x100px w