chromium/third_party/blink/web_tests/transitions/cross-fade-background-image.html

<!DOCTYPE>

<html>
<head>
    <style>
    .box {
        height: 200px;
        width: 200px;
        margin: 10px;
        -webkit-transition-duration: 1s;
        -webkit-transition-timing-function: linear;
    }

    #box {
        background-image: url('../fast/backgrounds/repeat/resources/gradient.gif');
        -webkit-transition-property: background-image;
    }

    #box.final {
        background-image: url('../fast/backgrounds/repeat/resources/nav.blue.gif');
    }

    #boxShorthand {
        background: url('../fast/backgrounds/repeat/resources/gradient.gif');
        -webkit-transition-property: background;
    }

    #boxShorthand.final {
        background: url('../fast/backgrounds/repeat/resources/nav.blue.gif');
    }

    #boxStatic {
        background-image: cross-fade(50% url('../fast/backgrounds/repeat/resources/gradient.gif'),
            url('../fast/backgrounds/repeat/resources/nav.blue.gif'));
    }

    </style>
    <script src="../animations/resources/animation-test-helpers.js" type="text/javascript"></script>
    <script>

    const expectedValues = [
    // [time, element-id, property, expected-value, tolerance]
    [0.5, ['box', 'boxStatic'], 'background-image', null, 0.05],
    [0.5, ['boxShorthand', 'boxStatic'], 'background-image', null, 0.05],
    ];

    function setupTest()
    {
        document.getElementById('box').className = 'box final';
        document.getElementById('boxShorthand').className = 'box final';
    }

    runTransitionTest(expectedValues, setupTest);
    </script>
</head>
<body>
    <div id="box" class="box"></div>
    <div id="boxShorthand" class="box"></div>
    <div id="boxStatic" class="box"></div>

    <div id="result"></div>
</body>
</html>