chromium/third_party/blink/web_tests/fast/scroll-behavior/overflow-hidden-scrollLeft.html

<!DOCTYPE html>
<html>
<head>
  <style>
    #container {
      width: 200px;
      height: 200px;
      overflow: hidden;
    }

    #content {
      width: 7500px;
      height: 7500px;
      background-color: blue;
    }
  </style>
  <script src="../../resources/testharness.js"></script>
  <script src="../../resources/testharnessreport.js"></script>
  <script src="resources/scroll-behavior-test.js"></script>
  <script type="text/javascript">
    function getEndPosition(testCase, startPosition) {
      var endPosition = {};
      endPosition.x = testCase.x;
      endPosition.y = startPosition.y;
      return endPosition;
    }

    function jsScroll(testCase) {
      var element = document.getElementById("container");
      element.scrollLeft = testCase.x;
    }

    const testScrolls = [
      {css: "auto", x: 1, y: 0},
      {css: "auto", x: 4, y: 0},
      {css: "smooth", waitForEnd: true, x: 20, y: 0},
      {css: "smooth", waitForEnd: true, x: 40, y: 0},
      {css: "smooth", waitForEnd: false, x: 4000, y: 0},
      {css: "smooth", waitForEnd: false, x: 10, y: 0},
    ];

    function doTest()
    {
      var testCases = [];
      for (var i = 0; i < testScrolls.length; i++) {
        testCases.push(new ScrollBehaviorTestCase(testScrolls[i]));
      }

      var element = document.getElementById("container");
      var scrollBehaviorTest = new ScrollBehaviorTest(element,
                                                      element,
                                                      testCases,
                                                      getEndPosition,
                                                      jsScroll);
      scrollBehaviorTest.run();
    }

    window.addEventListener('load', doTest, false);
  </script>
</head>

<body>
  <p>Test that setting scrollLeft on an overflow:hidden element works with both scroll behaviors</p>
  <div id="container">
    <div id="content"></div>
  </div>
</body>
</html>