diff --git a/services/core/java/com/android/server/hdmi/CecMessageBuffer.java b/services/core/java/com/android/server/hdmi/CecMessageBuffer.java
new file mode 100644
index 0000000000000..8f971fd7db071
--- /dev/null
+++ b/services/core/java/com/android/server/hdmi/CecMessageBuffer.java
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.hdmi;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Buffer for processing the incoming CEC messages while allocating logical addresses.
+ */
+final class CecMessageBuffer {
+    private List<HdmiCecMessage> mBuffer = new ArrayList<>();
+    private HdmiControlService mHdmiControlService;
+
+    CecMessageBuffer(HdmiControlService hdmiControlService) {
+        mHdmiControlService = hdmiControlService;
+    }
+
+    /**
+     * Adds a message to the buffer.
+     * Only certain types of messages need to be buffered.
+     * @param message The message to add to the buffer
+     * @return Whether the message was added to the buffer
+     */
+    public boolean bufferMessage(HdmiCecMessage message) {
+        switch (message.getOpcode()) {
+            case Constants.MESSAGE_ACTIVE_SOURCE:
+                bufferActiveSource(message);
+                return true;
+            case Constants.MESSAGE_IMAGE_VIEW_ON:
+            case Constants.MESSAGE_TEXT_VIEW_ON:
+                bufferImageOrTextViewOn(message);
+                return true;
+            case Constants.MESSAGE_SYSTEM_AUDIO_MODE_REQUEST:
+                bufferSystemAudioModeRequest(message);
+                return true;
+            // Add here if new message that needs to buffer
+            default:
+                // Do not need to buffer messages other than above
+                return false;
+        }
+    }
+
+    /**
+     * Process all messages in the buffer.
+     */
+    public void processMessages() {
+        for (final HdmiCecMessage message : mBuffer) {
+            mHdmiControlService.runOnServiceThread(new Runnable() {
+                @Override
+                public void run() {
+                    mHdmiControlService.handleCecCommand(message);
+                }
+            });
+        }
+        mBuffer.clear();
+    }
+
+    private void bufferActiveSource(HdmiCecMessage message) {
+        if (!replaceMessageIfBuffered(message, Constants.MESSAGE_ACTIVE_SOURCE)) {
+            mBuffer.add(message);
+        }
+    }
+
+    private void bufferImageOrTextViewOn(HdmiCecMessage message) {
+        if (!replaceMessageIfBuffered(message, Constants.MESSAGE_IMAGE_VIEW_ON)
+                && !replaceMessageIfBuffered(message, Constants.MESSAGE_TEXT_VIEW_ON)) {
+            mBuffer.add(message);
+        }
+    }
+
+    private void bufferSystemAudioModeRequest(HdmiCecMessage message) {
+        if (!replaceMessageIfBuffered(message, Constants.MESSAGE_SYSTEM_AUDIO_MODE_REQUEST)) {
+            mBuffer.add(message);
+        }
+    }
+
+    // Returns true if the message is replaced
+    private boolean replaceMessageIfBuffered(HdmiCecMessage message, int opcode) {
+        for (int i = 0; i < mBuffer.size(); i++) {
+            HdmiCecMessage bufferedMessage = mBuffer.get(i);
+            if (bufferedMessage.getOpcode() == opcode) {
+                mBuffer.set(i, message);
+                return true;
+            }
+        }
+        return false;
+    }
+}
diff --git a/services/core/java/com/android/server/hdmi/HdmiControlService.java b/services/core/java/com/android/server/hdmi/HdmiControlService.java
index fd825d6f62889..f3d0623f93f71 100644
--- a/services/core/java/com/android/server/hdmi/HdmiControlService.java
+++ b/services/core/java/com/android/server/hdmi/HdmiControlService.java
@@ -405,74 +405,7 @@ public class HdmiControlService extends SystemService {
     // Use getAtomWriter() instead of accessing directly, to allow dependency injection for testing.
     private HdmiCecAtomWriter mAtomWriter = new HdmiCecAtomWriter();
 
-    // Buffer for processing the incoming cec messages while allocating logical addresses.
-    private final class CecMessageBuffer {
-        private List<HdmiCecMessage> mBuffer = new ArrayList<>();
-
-        public boolean bufferMessage(HdmiCecMessage message) {
-            switch (message.getOpcode()) {
-                case Constants.MESSAGE_ACTIVE_SOURCE:
-                    bufferActiveSource(message);
-                    return true;
-                case Constants.MESSAGE_IMAGE_VIEW_ON:
-                case Constants.MESSAGE_TEXT_VIEW_ON:
-                    bufferImageOrTextViewOn(message);
-                    return true;
-                case Constants.MESSAGE_SYSTEM_AUDIO_MODE_REQUEST:
-                    bufferSystemAudioModeRequest(message);
-                    return true;
-                    // Add here if new message that needs to buffer
-                default:
-                    // Do not need to buffer messages other than above
-                    return false;
-            }
-        }
-
-        public void processMessages() {
-            for (final HdmiCecMessage message : mBuffer) {
-                runOnServiceThread(new Runnable() {
-                    @Override
-                    public void run() {
-                        handleCecCommand(message);
-                    }
-                });
-            }
-            mBuffer.clear();
-        }
-
-        private void bufferActiveSource(HdmiCecMessage message) {
-            if (!replaceMessageIfBuffered(message, Constants.MESSAGE_ACTIVE_SOURCE)) {
-                mBuffer.add(message);
-            }
-        }
-
-        private void bufferImageOrTextViewOn(HdmiCecMessage message) {
-            if (!replaceMessageIfBuffered(message, Constants.MESSAGE_IMAGE_VIEW_ON) &&
-                !replaceMessageIfBuffered(message, Constants.MESSAGE_TEXT_VIEW_ON)) {
-                mBuffer.add(message);
-            }
-        }
-
-        private void bufferSystemAudioModeRequest(HdmiCecMessage message) {
-            if (!replaceMessageIfBuffered(message, Constants.MESSAGE_SYSTEM_AUDIO_MODE_REQUEST)) {
-                mBuffer.add(message);
-            }
-        }
-
-        // Returns true if the message is replaced
-        private boolean replaceMessageIfBuffered(HdmiCecMessage message, int opcode) {
-            for (int i = 0; i < mBuffer.size(); i++) {
-                HdmiCecMessage bufferedMessage = mBuffer.get(i);
-                if (bufferedMessage.getOpcode() == opcode) {
-                    mBuffer.set(i, message);
-                    return true;
-                }
-            }
-            return false;
-        }
-    }
-
-    private final CecMessageBuffer mCecMessageBuffer = new CecMessageBuffer();
+    private CecMessageBuffer mCecMessageBuffer = new CecMessageBuffer(this);
 
     private final SelectRequestBuffer mSelectRequestBuffer = new SelectRequestBuffer();
 
@@ -988,6 +921,11 @@ public class HdmiControlService extends SystemService {
         mMessageValidator = messageValidator;
     }
 
+    @VisibleForTesting
+    void setCecMessageBuffer(CecMessageBuffer cecMessageBuffer) {
+        this.mCecMessageBuffer = cecMessageBuffer;
+    }
+
     /**
      * Returns {@link Looper} of main thread. Use this {@link Looper} instance
      * for tasks that are running on main service thread.