diff --git a/webrtc/RTCPeerConnection-helper.js b/webrtc/RTCPeerConnection-helper.js
index 24b3db7a0880fc..8a11a1ca1e9a00 100644
--- a/webrtc/RTCPeerConnection-helper.js
+++ b/webrtc/RTCPeerConnection-helper.js
@@ -582,7 +582,7 @@ const trackFactories = {
     return dst.stream.getAudioTracks()[0];
   },
 
-  video({width = 640, height = 480} = {}) {
+  video({width = 640, height = 480, signal = null} = {}) {
     const canvas = Object.assign(
       document.createElement("canvas"), {width, height}
     );
@@ -593,8 +593,13 @@ const trackFactories = {
     setInterval(() => {
       ctx.fillStyle = `rgb(${count%255}, ${count*count%255}, ${count%255})`;
       count += 1;
-
       ctx.fillRect(0, 0, width, height);
+      // If signal is set, add a constant-color box to the video frame.
+      if (signal !== null) {
+        ctx.fillStyle = `rgb(${signal}, ${signal}, ${signal})`;
+        ctx.fillRect(10, 10, 20, 20);
+        let pixel = ctx.getImageData(15, 15, 1, 1);
+      }
     }, 100);
 
     if (document.body) {
@@ -609,13 +614,40 @@ const trackFactories = {
   }
 };
 
+// Get the signal from a video element inserted by createNoiseStream
+function getVideoSignal(v) {
+  if (v.videoWidth < 21 || v.videoHeight < 21) {
+    return null;
+  }
+  const canvas = new OffscreenCanvas(v.videoWidth, v.videoHeight);
+  let context = canvas.getContext('2d');
+  context.drawImage(v, 0, 0, v.videoWidth, v.videoHeight);
+  // Extract pixel value at position 20, 20
+  let pixel = context.getImageData(20, 20, 1, 1);
+  return (pixel.data[0] + pixel.data[1] + pixel.data[2]) / 3;
+}
+
+function detectSignal(t, v, value) {
+  return new Promise((resolve) => {
+    let check = () => {
+      const signal = getVideoSignal(v);
+      if (signal !== null && signal < value + 1 && signal > value - 1) {
+        resolve();
+      } else {
+        t.step_timeout(check, 100);
+      }
+    }
+    check();
+  });
+}
+
 // Generate a MediaStream bearing the specified tracks.
 //
 // @param {object} [caps]
 // @param {boolean} [caps.audio] - flag indicating whether the generated stream
 //                                 should include an audio track
 // @param {boolean} [caps.video] - flag indicating whether the generated stream
-//                                 should include a video track
+//                                 should include a video track, or parameters for video
 async function getNoiseStream(caps = {}) {
   if (!trackFactories.canCreate(caps)) {
     return navigator.mediaDevices.getUserMedia(caps);
@@ -627,7 +659,7 @@ async function getNoiseStream(caps = {}) {
   }
 
   if (caps.video) {
-    tracks.push(trackFactories.video());
+    tracks.push(trackFactories.video(caps.video));
   }
 
   return new MediaStream(tracks);
diff --git a/webrtc/RTCRtpSender-replaceTrack.https.html b/webrtc/RTCRtpSender-replaceTrack.https.html
index a2c790b144e2de..671e86fd4e893a 100644
--- a/webrtc/RTCRtpSender-replaceTrack.https.html
+++ b/webrtc/RTCRtpSender-replaceTrack.https.html
@@ -272,5 +272,35 @@
                 without negotiating.
             3.  Queue a task that runs the following steps:
               1.  If connection's [[isClosed]] slot is true, abort these steps.
-   */
+  */
+
+promise_test(async t => {
+  const v = document.createElement('video');
+  v.autoplay = true;
+  const pc1 = new RTCPeerConnection();
+  t.add_cleanup(() => pc1.close());
+  const pc2 = new RTCPeerConnection();
+  t.add_cleanup(() => pc2.close());
+  const stream1 = await getNoiseStream({video: {signal: 20}});
+  t.add_cleanup(() => stream1.getTracks().forEach(track => track.stop()));
+  const [track1] = stream1.getTracks();
+  const stream2 = await getNoiseStream({video: {signal: 250}});
+  t.add_cleanup(() => stream2.getTracks().forEach(track => track.stop()));
+  const [track2] = stream2.getTracks();
+  const sender = pc1.addTrack(track1);
+  pc2.ontrack = (e) => {
+    v.srcObject = new MediaStream([e.track]);
+  };
+  const metadataToBeLoaded = new Promise((resolve) => {
+    v.addEventListener('loadedmetadata', () => {
+      resolve();
+    });
+  });
+  exchangeIceCandidates(pc1, pc2);
+  doSignalingHandshake(pc1, pc2);
+  await metadataToBeLoaded;
+  await detectSignal(t, v, 20);
+  await sender.replaceTrack(track2);
+  await detectSignal(t, v, 250);
+}, 'ReplaceTrack transmits the new track not the old track');
 </script>