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diff --git a/testing/web-platform/tests/css/css-contain/container-queries/transition-style-change-event.html b/testing/web-platform/tests/css/css-contain/container-queries/transition-style-change-event.html
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+<!doctype html>
+<meta charset="utf-8">
+<title>Container Queries - Style Change Event for transitions</title>
+<link rel="help" href="https://drafts.csswg.org/css-transitions/#starting">
+<link rel="help" href="https://drafts.csswg.org/css-contain-3/#animated-containers">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="support/cq-testcommon.js"></script>
+<style>
+  .container { container-type: size }
+  #outer {
+    width: 100px;
+    color: green;
+  }
+  @container (min-width: 200px) {
+    #inner { color: red }
+  }
+  @container (min-width: 400px) {
+    #target {
+      color: green;
+      transition: color 1s step-start;
+    }
+  }
+</style>
+<div id="outer" class="container">
+  <div id="inner" class="container">
+    <div id="target">Green</div>
+  </div>
+</div>
+</div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  const t = async_test("");
+  const event_handler = t.step_func_done((e) => {
+    assert_unreached("Transition event incorrectly triggered: " + e.type);
+  });
+  for (let event_name of ["transitionrun",
+                          "transitionstart",
+                          "transitionend",
+                          "transitioncancel"]) {
+    target.addEventListener(event_name, event_handler);
+  }
+
+  outer.offsetTop;
+  // #target is green. Making the #outer container 200px will turn #inner and
+  // #target red through inheritance.
+  outer.style.width = "200px";
+  // Making #inner 400px will make #target green.
+  inner.style.width = "400px";
+  // Both changes above should happen in one style change event and should not
+  // trigger any transition events. Run two rAFs to make sure any events have
+  // time to trigger.
+  requestAnimationFrame(() => requestAnimationFrame(t.step_func_done(() => {
+    assert_equals(getComputedStyle(inner).color, "rgb(255, 0, 0)",
+        "@container queries supported");
+  })));
+</script>