infrastructure/testdriver/actions/wheelScroll.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>TestDriver actions: wheel scroll</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-actions.js"></script>
<script src="/resources/testdriver-vendor.js"></script>

<style>
#container {
  width: 200px;
  height: 200px;
  overflow: scroll;
}

#content {
  width: 600px;
  height: 1000px;
  background-color: blue;
}

</style>

<div id="container">
  <div id="content"></div>
</div>

<script>
let event_type = [];
let event_id = [];

async_test(t => {
  let container = document.getElementById("container");
  container.addEventListener("wheel",
    e => {event_type.push(e.type);});

  let actions = new test_driver.Actions()
       .scroll(0, 0, 0, 50, {origin: container});

  actions.send()
    .then(t.step_func_done(() => {assert_array_equals(event_type, ["wheel"]);}))
    .catch(e => t.step_func(() => assert_unreached("Actions sequence failed " + e)));
});
</script>