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diff --git a/testing/web-platform/tests/html/rendering/non-replaced-elements/the-page/iframe-body-margin-attributes.html b/testing/web-platform/tests/html/rendering/non-replaced-elements/the-page/iframe-body-margin-attributes.html
new file mode 100644
index 0000000000..e1f4fb5154
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+++ b/testing/web-platform/tests/html/rendering/non-replaced-elements/the-page/iframe-body-margin-attributes.html
@@ -0,0 +1,32 @@
+<!doctype html>
+<title>iframe and body margin attributes</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<body marginwidth=20 marginheight=20 topmargin=10 rightmargin=10 bottommargin=10 leftmargin=10>
+<iframe data-desc="iframe marginwidth vs child body leftmargin" src="support/body-topmargin-leftmargin.html" marginwidth=10 marginheight=10></iframe>
+<iframe data-desc="iframe marginwidth vs child body marginwidth" src="support/body-marginwidth-marginheight.html" marginwidth=10 marginheight=10></iframe>
+<script>
+setup({explicit_done: true});
+
+onload = () => {
+  test(() => {
+    const style = getComputedStyle(document.body);
+    assert_style_props(style);
+  }, 'body marginwidth vs body leftmargin');
+
+  [].forEach.call(document.querySelectorAll('iframe'), iframe => {
+    test(() => {
+      const win = iframe.contentWindow;
+      const style = win.getComputedStyle(win.document.body);
+      assert_style_props(style);
+    }, iframe.dataset.desc);
+  });
+  done();
+}
+
+function assert_style_props(style) {
+  for (let prop of ['marginTop', 'marginRight', 'marginBottom', 'marginLeft']) {
+    assert_equals(style[prop], '20px', prop);
+  }
+}
+</script>