diff --git a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
index 09d08e4..d3a9128 100644
--- a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
@@ -647,6 +647,141 @@
              HdrDolbyVisionSupportedVariant<PrimaryDisplayVariant>>;
 
 /* ------------------------------------------------------------------------
+ *
+ * SurfaceFlinger::onHotplugReceived
+ */
+
+TEST_F(DisplayTransactionTest, hotplugEnqueuesEventsForDisplayTransaction) {
+    constexpr int currentSequenceId = 123;
+    constexpr hwc2_display_t displayId1 = 456;
+    constexpr hwc2_display_t displayId2 = 654;
+
+    // --------------------------------------------------------------------
+    // Preconditions
+
+    // Set the current sequence id for accepted events
+    mFlinger.mutableComposerSequenceId() = currentSequenceId;
+
+    // Set the main thread id so that the current thread does not appear to be
+    // the main thread.
+    mFlinger.mutableMainThreadId() = std::thread::id();
+
+    // --------------------------------------------------------------------
+    // Call Expectations
+
+    // We expect invalidate() to be invoked once to trigger display transaction
+    // processing.
+    EXPECT_CALL(*mMessageQueue, invalidate()).Times(1);
+
+    // --------------------------------------------------------------------
+    // Invocation
+
+    // Simulate two hotplug events (a connect and a disconnect)
+    mFlinger.onHotplugReceived(currentSequenceId, displayId1, HWC2::Connection::Connected);
+    mFlinger.onHotplugReceived(currentSequenceId, displayId2, HWC2::Connection::Disconnected);
+
+    // --------------------------------------------------------------------
+    // Postconditions
+
+    // The display transaction needed flag should be set.
+    EXPECT_TRUE(hasTransactionFlagSet(eDisplayTransactionNeeded));
+
+    // All events should be in the pending event queue.
+    const auto& pendingEvents = mFlinger.mutablePendingHotplugEvents();
+    ASSERT_EQ(2u, pendingEvents.size());
+    EXPECT_EQ(displayId1, pendingEvents[0].display);
+    EXPECT_EQ(HWC2::Connection::Connected, pendingEvents[0].connection);
+    EXPECT_EQ(displayId2, pendingEvents[1].display);
+    EXPECT_EQ(HWC2::Connection::Disconnected, pendingEvents[1].connection);
+}
+
+TEST_F(DisplayTransactionTest, hotplugDiscardsUnexpectedEvents) {
+    constexpr int currentSequenceId = 123;
+    constexpr int otherSequenceId = 321;
+    constexpr hwc2_display_t displayId = 456;
+
+    // --------------------------------------------------------------------
+    // Preconditions
+
+    // Set the current sequence id for accepted events
+    mFlinger.mutableComposerSequenceId() = currentSequenceId;
+
+    // Set the main thread id so that the current thread does not appear to be
+    // the main thread.
+    mFlinger.mutableMainThreadId() = std::thread::id();
+
+    // --------------------------------------------------------------------
+    // Call Expectations
+
+    // We do not expect any calls to invalidate().
+    EXPECT_CALL(*mMessageQueue, invalidate()).Times(0);
+
+    // --------------------------------------------------------------------
+    // Invocation
+
+    // Call with an unexpected sequence id
+    mFlinger.onHotplugReceived(otherSequenceId, displayId, HWC2::Connection::Invalid);
+
+    // --------------------------------------------------------------------
+    // Postconditions
+
+    // The display transaction needed flag should not be set
+    EXPECT_FALSE(hasTransactionFlagSet(eDisplayTransactionNeeded));
+
+    // There should be no pending events
+    EXPECT_TRUE(mFlinger.mutablePendingHotplugEvents().empty());
+}
+
+TEST_F(DisplayTransactionTest, hotplugProcessesEnqueuedEventsIfCalledOnMainThread) {
+    constexpr int currentSequenceId = 123;
+    constexpr hwc2_display_t displayId1 = 456;
+
+    // --------------------------------------------------------------------
+    // Note:
+    // --------------------------------------------------------------------
+    // This test case is a bit tricky. We want to verify that
+    // onHotplugReceived() calls processDisplayHotplugEventsLocked(), but we
+    // don't really want to provide coverage for everything the later function
+    // does as there are specific tests for it.
+    // --------------------------------------------------------------------
+
+    // --------------------------------------------------------------------
+    // Preconditions
+
+    // Set the current sequence id for accepted events
+    mFlinger.mutableComposerSequenceId() = currentSequenceId;
+
+    // Set the main thread id so that the current thread does appear to be the
+    // main thread.
+    mFlinger.mutableMainThreadId() = std::this_thread::get_id();
+
+    // --------------------------------------------------------------------
+    // Call Expectations
+
+    // We expect invalidate() to be invoked once to trigger display transaction
+    // processing.
+    EXPECT_CALL(*mMessageQueue, invalidate()).Times(1);
+
+    // --------------------------------------------------------------------
+    // Invocation
+
+    // Simulate a disconnect on a display id that is not connected. This should
+    // be enqueued by onHotplugReceived(), and dequeued by
+    // processDisplayHotplugEventsLocked(), but then ignored as invalid.
+    mFlinger.onHotplugReceived(currentSequenceId, displayId1, HWC2::Connection::Disconnected);
+
+    // --------------------------------------------------------------------
+    // Postconditions
+
+    // The display transaction needed flag should be set.
+    EXPECT_TRUE(hasTransactionFlagSet(eDisplayTransactionNeeded));
+
+    // There should be no event queued on return, as it should have been
+    // processed.
+    EXPECT_TRUE(mFlinger.mutablePendingHotplugEvents().empty());
+}
+
+/* ------------------------------------------------------------------------
  * SurfaceFlinger::setupNewDisplayDeviceInternal
  */
 
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index 2fafd70..0a06702 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -72,6 +72,11 @@
         return mFlinger->handleTransactionLocked(transactionFlags);
     }
 
+    auto onHotplugReceived(int32_t sequenceId, hwc2_display_t display,
+                           HWC2::Connection connection) {
+        return mFlinger->onHotplugReceived(sequenceId, display, connection);
+    }
+
     /* ------------------------------------------------------------------------
      * Read-write access to private data to set up preconditions and assert
      * post-conditions.
@@ -88,10 +93,12 @@
     auto& mutableEventQueue() { return mFlinger->mEventQueue; }
     auto& mutableEventThread() { return mFlinger->mEventThread; }
     auto& mutableInterceptor() { return mFlinger->mInterceptor; }
+    auto& mutableMainThreadId() { return mFlinger->mMainThreadId; }
     auto& mutablePendingHotplugEvents() { return mFlinger->mPendingHotplugEvents; }
     auto& mutableTransactionFlags() { return mFlinger->mTransactionFlags; }
     auto& mutableUseHwcVirtualDisplays() { return mFlinger->mUseHwcVirtualDisplays; }
 
+    auto& mutableComposerSequenceId() { return mFlinger->getBE().mComposerSequenceId; }
     auto& mutableHwcDisplayData() { return mFlinger->getBE().mHwc->mDisplayData; }
     auto& mutableHwcDisplaySlots() { return mFlinger->getBE().mHwc->mHwcDisplaySlots; }