diff --git a/services/surfaceflinger/tests/unittests/SchedulerTest.cpp b/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
index 4c6539e..e515895 100644
--- a/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
+++ b/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
@@ -608,6 +608,85 @@
                                              TimePoint::fromNs(4500)));
 }
 
+TEST_F(SchedulerTest, resyncAllToHardwareVsync) FTL_FAKE_GUARD(kMainThreadContext) {
+    // resyncAllToHardwareVsync will result in requesting hardware VSYNC on both displays, since
+    // they are both on.
+    EXPECT_CALL(mScheduler->mockRequestHardwareVsync, Call(kDisplayId1, true)).Times(1);
+    EXPECT_CALL(mScheduler->mockRequestHardwareVsync, Call(kDisplayId2, true)).Times(1);
+
+    mScheduler->registerDisplay(kDisplayId2,
+                                std::make_shared<RefreshRateSelector>(kDisplay2Modes,
+                                                                      kDisplay2Mode60->getId()));
+    mScheduler->setDisplayPowerMode(kDisplayId1, hal::PowerMode::ON);
+    mScheduler->setDisplayPowerMode(kDisplayId2, hal::PowerMode::ON);
+
+    static constexpr bool kDisallow = true;
+    mScheduler->disableHardwareVsync(kDisplayId1, kDisallow);
+    mScheduler->disableHardwareVsync(kDisplayId2, kDisallow);
+
+    static constexpr bool kAllowToEnable = true;
+    mScheduler->resyncAllToHardwareVsync(kAllowToEnable);
+}
+
+TEST_F(SchedulerTest, resyncAllDoNotAllow) FTL_FAKE_GUARD(kMainThreadContext) {
+    // Without setting allowToEnable to true, resyncAllToHardwareVsync does not
+    // result in requesting hardware VSYNC.
+    EXPECT_CALL(mScheduler->mockRequestHardwareVsync, Call(kDisplayId1, _)).Times(0);
+
+    mScheduler->setDisplayPowerMode(kDisplayId1, hal::PowerMode::ON);
+
+    static constexpr bool kDisallow = true;
+    mScheduler->disableHardwareVsync(kDisplayId1, kDisallow);
+
+    static constexpr bool kAllowToEnable = false;
+    mScheduler->resyncAllToHardwareVsync(kAllowToEnable);
+}
+
+TEST_F(SchedulerTest, resyncAllSkipsOffDisplays) FTL_FAKE_GUARD(kMainThreadContext) {
+    SET_FLAG_FOR_TEST(flags::multithreaded_present, true);
+
+    // resyncAllToHardwareVsync will result in requesting hardware VSYNC on display 1, which is on,
+    // but not on display 2, which is off.
+    EXPECT_CALL(mScheduler->mockRequestHardwareVsync, Call(kDisplayId1, true)).Times(1);
+    EXPECT_CALL(mScheduler->mockRequestHardwareVsync, Call(kDisplayId2, _)).Times(0);
+
+    mScheduler->setDisplayPowerMode(kDisplayId1, hal::PowerMode::ON);
+
+    mScheduler->registerDisplay(kDisplayId2,
+                                std::make_shared<RefreshRateSelector>(kDisplay2Modes,
+                                                                      kDisplay2Mode60->getId()));
+    ASSERT_EQ(hal::PowerMode::OFF, mScheduler->getDisplayPowerMode(kDisplayId2));
+
+    static constexpr bool kDisallow = true;
+    mScheduler->disableHardwareVsync(kDisplayId1, kDisallow);
+    mScheduler->disableHardwareVsync(kDisplayId2, kDisallow);
+
+    static constexpr bool kAllowToEnable = true;
+    mScheduler->resyncAllToHardwareVsync(kAllowToEnable);
+}
+
+TEST_F(SchedulerTest, resyncAllLegacyAppliesToOffDisplays) FTL_FAKE_GUARD(kMainThreadContext) {
+    SET_FLAG_FOR_TEST(flags::multithreaded_present, false);
+
+    // In the legacy code, prior to the flag, resync applied to OFF displays.
+    EXPECT_CALL(mScheduler->mockRequestHardwareVsync, Call(kDisplayId1, true)).Times(1);
+    EXPECT_CALL(mScheduler->mockRequestHardwareVsync, Call(kDisplayId2, true)).Times(1);
+
+    mScheduler->setDisplayPowerMode(kDisplayId1, hal::PowerMode::ON);
+
+    mScheduler->registerDisplay(kDisplayId2,
+                                std::make_shared<RefreshRateSelector>(kDisplay2Modes,
+                                                                      kDisplay2Mode60->getId()));
+    ASSERT_EQ(hal::PowerMode::OFF, mScheduler->getDisplayPowerMode(kDisplayId2));
+
+    static constexpr bool kDisallow = true;
+    mScheduler->disableHardwareVsync(kDisplayId1, kDisallow);
+    mScheduler->disableHardwareVsync(kDisplayId2, kDisallow);
+
+    static constexpr bool kAllowToEnable = true;
+    mScheduler->resyncAllToHardwareVsync(kAllowToEnable);
+}
+
 class AttachedChoreographerTest : public SchedulerTest {
 protected:
     void frameRateTestScenario(Fps layerFps, int8_t frameRateCompatibility, Fps displayFps,
diff --git a/services/surfaceflinger/tests/unittests/TestableScheduler.h b/services/surfaceflinger/tests/unittests/TestableScheduler.h
index b036e99..2a1b88e 100644
--- a/services/surfaceflinger/tests/unittests/TestableScheduler.h
+++ b/services/surfaceflinger/tests/unittests/TestableScheduler.h
@@ -115,6 +115,15 @@
         Scheduler::setPacesetterDisplay(displayId);
     }
 
+    std::optional<hal::PowerMode> getDisplayPowerMode(PhysicalDisplayId id) {
+        ftl::FakeGuard guard1(kMainThreadContext);
+        ftl::FakeGuard guard2(mDisplayLock);
+        return mDisplays.get(id).transform(
+                [](const Display& display) { return display.powerMode; });
+    }
+
+    using Scheduler::resyncAllToHardwareVsync;
+
     auto& mutableAppConnectionHandle() { return mAppConnectionHandle; }
     auto& mutableLayerHistory() { return mLayerHistory; }
     auto& mutableAttachedChoreographers() { return mAttachedChoreographers; }