<svg xmlns="http://www.w3.org/2000/svg">
    <text dominant-baseline="hanging" x="20" y="40" font-size="44px">
        Foo
        <animate id="down1" attributeName="y" fill="freeze" begin="indefinite" dur="20ms" to="140"/>
        <animate id="up1" attributeName="y" fill="freeze" begin="indefinite" dur="20ms" to="40"/>
    </text>
    <line x1="200" y1="60" x2="300" y2="60" stroke="green" stroke-width="100">
        <animate id="down2" attributeName="y1" fill="freeze" begin="indefinite" dur="20ms" to="160"/>
        <animate id="up2" attributeName="y1" fill="freeze" begin="indefinite" dur="20ms" to="60"/>

        <animate id="down3" attributeName="y2" fill="freeze" begin="indefinite" dur="20ms" to="160"/>
        <animate id="up3" attributeName="y2" fill="freeze" begin="indefinite" dur="20ms" to="60"/>
    </line>
    <marker id="Rectangle" viewBox="0 0 100 100" refX="100" refY="50" markerWidth="100" markerHeight="100" orient="0deg">
        <rect width="100" height="100" fill="green"/>
        <animate id="down4" attributeName="orient" fill="freeze" begin="indefinite" dur="20ms" from="0deg" to="180deg"/>
        <animate id="up4" attributeName="orient" fill="freeze" begin="indefinite" dur="20ms" from="180deg" to="0deg"/>
    </marker>
    <line x1="400" y1="160" x2="450" y2="160" stroke-width="1" stroke="white"  marker-end="url(#Rectangle)"/>
    <script type="text/javascript">
    <![CDATA[
        if (window.testRunner)
            testRunner.waitUntilDone();

        var groups = [
            { down: "down1", up: "up1" },
            { down: "down2", up: "up2" },
            { down: "down3", up: "up3" },
            { down: "down4", up: "up4" },
        ];

        var downCount = 0;
        var upCount = 0;

        for (let group of groups) {
            let down = document.getElementById(group.down);
            let up = document.getElementById(group.up);

            down.addEventListener("endEvent", () => {
                if (++downCount <= groups.length)
                    toggle(up);

                if (window.testRunner) {
                    if (downCount == groups.length * 2)
                        testRunner.notifyDone();
                }
            });

            up.addEventListener("endEvent", () => {
                if (++upCount <= groups.length)
                    toggle(down);
            });

            down.beginElement();
        }

        function toggle(newElement) {
            newElement.beginElement();
        }
    ]]>
    </script>
</svg>