diff --git a/fetch/fetch-later/send-on-deactivate.tentative.https.window.js b/fetch/fetch-later/send-on-deactivate.tentative.https.window.js
index 173c95ac12037c1..94877e8321a768f 100644
--- a/fetch/fetch-later/send-on-deactivate.tentative.https.window.js
+++ b/fetch/fetch-later/send-on-deactivate.tentative.https.window.js
@@ -9,6 +9,11 @@
 
 'use strict';
 
+// NOTE: Due to the restriction of WPT runner, the following tests are all run
+// with BackgroundSync off, which is different from some browsers,
+// e.g. Chrome, default behavior, as the testing infra does not support enabling
+// it.
+
 parallelPromiseTest(async t => {
   const uuid = token();
   const url = generateSetBeaconURL(uuid);
@@ -29,15 +34,19 @@ parallelPromiseTest(async t => {
   }, [url]);
   // Navigates away to let page enter BFCache.
   const rc2 = await rc1.navigateToNew();
-  // Navigate back.
+  // Navigates back.
   await rc2.historyBack();
-  // Verify that the page was BFCached.
+  // Verifies the page was BFCached.
   assert_true(await rc1.executeScript(() => {
     return window.pageshowEvent.persisted;
   }));
 
-  await expectBeacon(uuid, {count: 0});
-}, `fetchLater() does not send on page entering BFCache.`);
+  // Theoretically, the request should still be pending thus 0 request received.
+  // However, 1 request is sent, as by default the WPT test runner, e.g.
+  // content_shell in Chromium, does not enable BackgroundSync permission,
+  // resulting in forcing request sending on every navigation.
+  await expectBeacon(uuid, {count: 1});
+}, `fetchLater() sends on page entering BFCache if BackgroundSync is off.`);
 
 parallelPromiseTest(async t => {
   const uuid = token();
@@ -47,7 +56,7 @@ parallelPromiseTest(async t => {
   const rc1 = await helper.addWindow(
       /*config=*/ null, /*options=*/ {features: 'noopener'});
 
-  // When the remote is BFCached, creates a fetchLater request w/
+  // When the remote is put into BFCached, creates a fetchLater request w/
   // activateAfter = 0s. It should be sent out immediately.
   await rc1.executeScript(url => {
     window.addEventListener('pagehide', e => {
@@ -62,13 +71,14 @@ parallelPromiseTest(async t => {
   }, [url]);
   // Navigates away to trigger request sending.
   const rc2 = await rc1.navigateToNew();
-  // Navigate back.
+  // Navigates back.
   await rc2.historyBack();
-  // Verify that the page was BFCached.
+  // Verifies the page was BFCached.
   assert_true(await rc1.executeScript(() => {
     return window.pageshowEvent.persisted;
   }));
 
+  // NOTE: In this case, it does not matter if BackgroundSync is on or off.
   await expectBeacon(uuid, {count: 1});
 }, `Call fetchLater() when BFCached with activateAfter=0 sends immediately.`);
 
@@ -92,13 +102,14 @@ parallelPromiseTest(async t => {
   }, [url]);
   // Navigates away to trigger request sending.
   const rc2 = await rc1.navigateToNew();
-  // Navigate back.
+  // Navigates back.
   await rc2.historyBack();
-  // Verify that the page was NOT BFCached.
+  // Verifies the page was NOT BFCached.
   assert_equals(undefined, await rc1.executeScript(() => {
     return window.pageshowEvent;
   }));
 
+  // NOTE: In this case, it does not matter if BackgroundSync is on or off.
   await expectBeacon(uuid, {count: 1});
 }, `fetchLater() sends on navigating away a page w/o BFCache.`);
 
@@ -125,12 +136,50 @@ parallelPromiseTest(async t => {
   }, [url]);
   // Navigates away to trigger request sending.
   const rc2 = await rc1.navigateToNew();
-  // Navigate back.
+  // Navigates back.
   await rc2.historyBack();
-  // Verify that the page was NOT BFCached.
+  // Verifies the page was NOT BFCached.
   assert_equals(undefined, await rc1.executeScript(() => {
     return window.pageshowEvent;
   }));
 
+  // NOTE: In this case, it does not matter if BackgroundSync is on or off.
   await expectBeacon(uuid, {count: 1});
 }, `fetchLater() does not send aborted request on navigating away a page w/o BFCache.`);
+
+parallelPromiseTest(async t => {
+  const uuid = token();
+  const url = generateSetBeaconURL(uuid);
+  const options = {activateAfter: 60000};
+  const helper = new RemoteContextHelper();
+  // Opens a window with noopener so that BFCache will work.
+  const rc1 = await helper.addWindow(
+      /*config=*/ null, /*options=*/ {features: 'noopener'});
+
+  // Creates a fetchLater request in remote which should only be sent on
+  // navigating away.
+  await rc1.executeScript((url) => {
+    // Sets activateAfter = 1m to indicate the request should NOT be sent out
+    // immediately.
+    fetchLater(url, {activateAfter: 60000});
+    // Adds a pageshow listener to stash the BFCache event.
+    window.addEventListener('pageshow', e => {
+      window.pageshowEvent = e;
+    });
+  }, [url]);
+  // Navigates away to trigger request sending.
+  const rc2 = await rc1.navigateToNew();
+  // Navigates back.
+  await rc2.historyBack();
+  // Verifies the page was BFCached.
+  assert_true(await rc1.executeScript(() => {
+    return window.pageshowEvent.persisted;
+  }));
+
+  // Theoretically, the request should still be pending thus 0 request received.
+  // However, 1 request is sent, as by default the WPT test runner, e.g.
+  // content_shell in Chromium, does not enable BackgroundSync permission,
+  // resulting in forcing request sending on every navigation, even if page is
+  // put into BFCache.
+  await expectBeacon(uuid, {count: 1});
+}, `fetchLater() with activateAfter=1m sends on page entering BFCache if BackgroundSync is off.`);