1 files changed, 39 insertions, 0 deletions
diff --git a/layout/reftests/css-animations/stacking-context-transform-wins-over-transition.html b/layout/reftests/css-animations/stacking-context-transform-wins-over-transition.html
new file mode 100644
index 0000000000..8d1de575e0
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+++ b/layout/reftests/css-animations/stacking-context-transform-wins-over-transition.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<html class="reftest-wait">
+<title>
+Transform animation winning over transition creates a stacking context
+for correct style
+</title>
+<style>
+span {
+  height: 100px;
+  width: 100px;
+  position: fixed;
+  background: green;
+  top: 50px;
+}
+@keyframes TransformNone {
+  from, to { transform: none; }
+}
+#test {
+  width: 100px; height: 100px;
+  background: blue;
+  transform: translateX(200px);
+  transition: transform 100s steps(1, start);
+  animation: TransformNone 100s;
+}
+</style>
+<span></span>
+<div id="test"></div>
+<script>
+window.addEventListener("load", () => {
+  var target = document.getElementById("test");
+  getComputedStyle(target).transform;
+
+  // CSS animation wins over transition, so transition won't be visible during
+  // the CSS animation.
+  target.style.transform = "translateX(100px)";
+  getComputedStyle(target).transform;
+  document.documentElement.classList.remove("reftest-wait");
+});
+</script>