diff --git a/media/libmedia/IMediaPlayer.cpp b/media/libmedia/IMediaPlayer.cpp
index 8a4b17c..60e8f87 100644
--- a/media/libmedia/IMediaPlayer.cpp
+++ b/media/libmedia/IMediaPlayer.cpp
@@ -34,54 +34,6 @@
 
 using media::VolumeShaper;
 
-enum {
-    DISCONNECT = IBinder::FIRST_CALL_TRANSACTION,
-    SET_DATA_SOURCE_URL,
-    SET_DATA_SOURCE_FD,
-    SET_DATA_SOURCE_STREAM,
-    SET_DATA_SOURCE_CALLBACK,
-    SET_DATA_SOURCE_RTP,
-    SET_BUFFERING_SETTINGS,
-    GET_BUFFERING_SETTINGS,
-    PREPARE_ASYNC,
-    START,
-    STOP,
-    IS_PLAYING,
-    SET_PLAYBACK_SETTINGS,
-    GET_PLAYBACK_SETTINGS,
-    SET_SYNC_SETTINGS,
-    GET_SYNC_SETTINGS,
-    PAUSE,
-    SEEK_TO,
-    GET_CURRENT_POSITION,
-    GET_DURATION,
-    RESET,
-    NOTIFY_AT,
-    SET_AUDIO_STREAM_TYPE,
-    SET_LOOPING,
-    SET_VOLUME,
-    INVOKE,
-    SET_METADATA_FILTER,
-    GET_METADATA,
-    SET_AUX_EFFECT_SEND_LEVEL,
-    ATTACH_AUX_EFFECT,
-    SET_VIDEO_SURFACETEXTURE,
-    SET_PARAMETER,
-    GET_PARAMETER,
-    SET_RETRANSMIT_ENDPOINT,
-    GET_RETRANSMIT_ENDPOINT,
-    SET_NEXT_PLAYER,
-    APPLY_VOLUME_SHAPER,
-    GET_VOLUME_SHAPER_STATE,
-    // Modular DRM
-    PREPARE_DRM,
-    RELEASE_DRM,
-    // AudioRouting
-    SET_OUTPUT_DEVICE,
-    GET_ROUTED_DEVICE_ID,
-    ENABLE_AUDIO_DEVICE_CALLBACK,
-};
-
 // ModDrm helpers
 static void readVector(const Parcel& reply, Vector<uint8_t>& vector) {
     uint32_t size = reply.readUint32();
diff --git a/media/libmedia/include/media/IMediaPlayer.h b/media/libmedia/include/media/IMediaPlayer.h
index 3548a1e..28684d1 100644
--- a/media/libmedia/include/media/IMediaPlayer.h
+++ b/media/libmedia/include/media/IMediaPlayer.h
@@ -137,6 +137,56 @@
     virtual status_t        setOutputDevice(audio_port_handle_t deviceId) = 0;
     virtual status_t        getRoutedDeviceId(audio_port_handle_t *deviceId) = 0;
     virtual status_t        enableAudioDeviceCallback(bool enabled) = 0;
+protected:
+
+    friend class IMediaPlayerTest;
+    enum {
+        DISCONNECT = IBinder::FIRST_CALL_TRANSACTION,
+        SET_DATA_SOURCE_URL,
+        SET_DATA_SOURCE_FD,
+        SET_DATA_SOURCE_STREAM,
+        SET_DATA_SOURCE_CALLBACK,
+        SET_DATA_SOURCE_RTP,
+        SET_BUFFERING_SETTINGS,
+        GET_BUFFERING_SETTINGS,
+        PREPARE_ASYNC,
+        START,
+        STOP,
+        IS_PLAYING,
+        SET_PLAYBACK_SETTINGS,
+        GET_PLAYBACK_SETTINGS,
+        SET_SYNC_SETTINGS,
+        GET_SYNC_SETTINGS,
+        PAUSE,
+        SEEK_TO,
+        GET_CURRENT_POSITION,
+        GET_DURATION,
+        RESET,
+        NOTIFY_AT,
+        SET_AUDIO_STREAM_TYPE,
+        SET_LOOPING,
+        SET_VOLUME,
+        INVOKE,
+        SET_METADATA_FILTER,
+        GET_METADATA,
+        SET_AUX_EFFECT_SEND_LEVEL,
+        ATTACH_AUX_EFFECT,
+        SET_VIDEO_SURFACETEXTURE,
+        SET_PARAMETER,
+        GET_PARAMETER,
+        SET_RETRANSMIT_ENDPOINT,
+        GET_RETRANSMIT_ENDPOINT,
+        SET_NEXT_PLAYER,
+        APPLY_VOLUME_SHAPER,
+        GET_VOLUME_SHAPER_STATE,
+        // Modular DRM
+        PREPARE_DRM,
+        RELEASE_DRM,
+        // AudioRouting
+        SET_OUTPUT_DEVICE,
+        GET_ROUTED_DEVICE_ID,
+        ENABLE_AUDIO_DEVICE_CALLBACK,
+    };
 };
 
 // ----------------------------------------------------------------------------
diff --git a/media/libmedia/tests/mediaplayer/Android.bp b/media/libmedia/tests/mediaplayer/Android.bp
new file mode 100644
index 0000000..5538ea0
--- /dev/null
+++ b/media/libmedia/tests/mediaplayer/Android.bp
@@ -0,0 +1,39 @@
+/*
+ * Copyright 2021 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.
+ */
+
+cc_test {
+    name: "IMediaPlayerTest",
+    test_suites: ["device-tests", "mts"],
+    gtest: true,
+
+    srcs: [
+        "IMediaPlayerTest.cpp",
+    ],
+
+    shared_libs: [
+        "libbinder",
+        "liblog",
+        "libmedia",
+        "libstagefright",
+        "libstagefright_foundation",
+        "libutils",
+    ],
+    compile_multilib: "first",
+    cflags: [
+        "-Werror",
+        "-Wall",
+    ],
+}
diff --git a/media/libmedia/tests/mediaplayer/IMediaPlayerTest.cpp b/media/libmedia/tests/mediaplayer/IMediaPlayerTest.cpp
new file mode 100644
index 0000000..cc60933
--- /dev/null
+++ b/media/libmedia/tests/mediaplayer/IMediaPlayerTest.cpp
@@ -0,0 +1,73 @@
+/*
+ * Copyright 2021 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.
+ */
+
+#include <binder/IServiceManager.h>
+#include <binder/Parcel.h>
+#include <gtest/gtest.h>
+#include <media/stagefright/foundation/ABuffer.h>
+#include <media/IMediaPlayer.h>
+#include <media/IMediaPlayerService.h>
+#include <media/mediaplayer.h>
+
+namespace android {
+
+constexpr uint8_t kMockByteArray[16] = {};
+
+ class IMediaPlayerTest : public testing::Test {
+  protected:
+   static constexpr uint32_t PREPARE_DRM = IMediaPlayer::PREPARE_DRM;
+
+   void SetUp() override {
+    mediaPlayer_ = sp<MediaPlayer>::make();
+    sp<IServiceManager> serviceManager = defaultServiceManager();
+    sp<IBinder> mediaPlayerService = serviceManager->getService(String16("media.player"));
+    sp<IMediaPlayerService> iMediaPlayerService =
+            IMediaPlayerService::asInterface(mediaPlayerService);
+    iMediaPlayer_ = iMediaPlayerService->create(mediaPlayer_);
+   }
+
+   sp<MediaPlayer> mediaPlayer_;
+   sp<IMediaPlayer> iMediaPlayer_;
+ };
+
+TEST_F(IMediaPlayerTest, PrepareDrmInvalidTransaction) {
+    Parcel data, reply;
+    data.writeInterfaceToken(iMediaPlayer_->getInterfaceDescriptor());
+    data.write(kMockByteArray, 16);
+
+    // We write a length greater than the following session id array. Should be discarded.
+    data.writeUint32(2);
+    data.writeUnpadded(kMockByteArray, 1);
+
+    status_t result = IMediaPlayer::asBinder(iMediaPlayer_)
+            ->transact(PREPARE_DRM, data, &reply);
+    ASSERT_EQ(result, BAD_VALUE);
+}
+
+TEST_F(IMediaPlayerTest, PrepareDrmValidTransaction) {
+    Parcel data, reply;
+    data.writeInterfaceToken(iMediaPlayer_->getInterfaceDescriptor());
+    data.write(kMockByteArray, 16);
+
+    // We write a length equal to the length of the following data. The transaction should be valid.
+    data.writeUint32(1);
+    data.write(kMockByteArray, 1);
+
+    status_t result = IMediaPlayer::asBinder(iMediaPlayer_)
+            ->transact(PREPARE_DRM, data, &reply);
+    ASSERT_EQ(result, OK);
+}
+}  // namespace android