1 files changed, 38 insertions, 0 deletions
diff --git a/testing/web-platform/tests/largest-contentful-paint/update-on-style-change.tentative.html b/testing/web-platform/tests/largest-contentful-paint/update-on-style-change.tentative.html
new file mode 100644
index 0000000000..dd34e61b0f
--- /dev/null
+++ b/testing/web-platform/tests/largest-contentful-paint/update-on-style-change.tentative.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>LargestContentfulPaint entries should generate for updates to previous LargestContentfulPaint nodes.</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+
+<body>
+  <script>
+    promise_test(() => {
+      assert_implements(window.LargestContentfulPaint, "LargestContentfulPaint is not implemented");
+      let countLcp = 0;
+      let firstLcp = null;
+      const timeoutPromise = new Promise(resolve => step_timeout(() => {
+        resolve(new Error('Did not observe two LCP entries'))
+      }, 3 * 1000));
+      const testPromise = new Promise(resolve => {
+        new PerformanceObserver(list => {
+          const entries = list.getEntries();
+          for (const entry of entries) {
+            ++countLcp;
+            assert_equals(entry.entryType, 'largest-contentful-paint');
+            assert_equals(entry.id, 'text');
+            if (countLcp == 1) {
+              firstLcp = entry;
+            } else if (countLcp == 2) {
+              assert_more_than(entry.startTime, firstLcp.startTime);
+              assert_more_than(entry.size, firstLcp.size);
+              resolve();
+            }
+          }
+        }).observe({ entryTypes: ['largest-contentful-paint'] });
+      });
+      return Promise.race([timeoutPromise, testPromise]);
+    })
+  </script>
+  <div id="text">text</div>
+  <link rel="stylesheet" href="/resources/slow-style-change.py">
+</body>