<style>
test {
    transition: 5s;
    display: block;
    height: 100px;
    border: 2px solid green;
    transition-timing-function: steps(2, start);
}
.animate { display:inline-block; height:10px; width:10px; }
</style>
<test></test>
<script>
if (window.testRunner)
    testRunner.waitUntilDone();

const test = document.querySelector("test");

function tryComplete()
{
    if (test.offsetHeight < 100) {
        if (window.testRunner)
            testRunner.notifyDone();
        return;
    }
    setTimeout(tryComplete, 10);
}

test.offsetWidth;
test.className = "animate";
tryComplete();
</script>