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diff --git a/testing/web-platform/tests/css/css-scroll-snap/scroll-margin.html b/testing/web-platform/tests/css/css-scroll-snap/scroll-margin.html
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+++ b/testing/web-platform/tests/css/css-scroll-snap/scroll-margin.html
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+<!DOCTYPE html>
+<link rel="help" href="https://drafts.csswg.org/css-scroll-snap-1/#scroll-margin" />
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<style>
+div {
+  position: absolute;
+  margin: 0px;
+}
+#scroller {
+  height: 500px;
+  width: 500px;
+  overflow: hidden;
+  scroll-snap-type: both mandatory;
+}
+#target {
+  width: 300px;
+  height: 300px;
+  background-color: blue;
+}
+#another-target {
+  width: 300px;
+  height: 300px;
+  top: 400px;
+  left: 400px;
+  background-color: blue;
+  scroll-snap-align: start;
+}
+</style>
+
+<div id="scroller">
+  <div style="width: 2000px; height: 2000px;"></div>
+  <div id="target"></div>
+  <div id="another-target"></div>
+</div>
+
+<script>
+test(() => {
+  target.style.scrollSnapAlign = "start";
+  target.style.scrollMargin = "100px";
+  target.style.left = "300px";
+  target.style.top = "300px";
+
+  scroller.scrollTo(0, 0);
+  // `target position (300px, 300px)` - `margin (100px, 100px)`.
+  assert_equals(scroller.scrollLeft, 200);
+  assert_equals(scroller.scrollTop, 200);
+
+  target.style.scrollSnapAlign = "end";
+
+  // `target position (300px, 300px)` + `target size (300px, 300px) +
+  // `margin (100px, 100px) - `scroller size (500px, 500px)`.
+  scroller.scrollTo(0, 0);
+  assert_equals(scroller.scrollLeft, 200);
+  assert_equals(scroller.scrollTop, 200);
+}, "Snaps to the positions adjusted by scroll-margin");
+
+test(() => {
+  target.style.left = "0px";
+  target.style.top = "0px";
+  target.style.scrollSnapAlign = "start";
+
+  // Since the target is at (0px, 0px) in the scroll port, the added margin
+  // should not be considered, and the snap points for this snap area should be
+  // the closest points in the scroll port (i.e x=0 or y=0).
+  target.style.scrollMargin = "200px";
+
+  // Distance from target without margin:
+  // `scroll position (150px, 150px)` - `target position (0px, 0px)`
+  // = (150px, 150px)
+  //
+  // Distance from target with margin:
+  // `scroll position (150px, 150px)` - [`target position (0px, 0px)` -
+  // `target margin (200px, 200px)`]
+  // = (350px, 350px)
+  //
+  // Distance from other target:
+  // `other target position (400px, 400px)` - `scroll position (150px, 150px)`
+  // = (250px, 250px)
+  //
+  // Therefore if the "out-of-scrollport" scroll-margin contributes to the
+  // calculation, then the other target would be snapped to. However if the
+  // scroll-margin is not considered, then the (0px, 0px) target should be
+  // snapped to.
+  scroller.scrollTo(150, 150);
+  assert_equals(scroller.scrollLeft, 0);
+  assert_equals(scroller.scrollTop, 0);
+}, "scroll-margin doesn't contribute to the snap position of the element " +
+   "if it's outside of the scroll port");
+</script>