Follow practices/guidance in Muxer tests around:

* @Before and @After usage. [1].
* static fields before non-static. [2].

@Before method should typically be paired with an @After method,
focused on ensuring that the component is released regardless of what
the test does.

In tests, inlining final class variables is preferrable [1]. In general
things like the file path should be part of the test (the @Rule means
we don't need before/after) if only used once.

Statically importing values and using them directly is preferable to
having a variable declared as non-final that's effectively final,
because from a readability perspective someone can see (the caps) that
the value is final static and immutable, so doesn't have to check if
it's changed/reassigned.

PiperOrigin-RevId: 586697887

libraries/muxer/src/test/java/androidx/media3/muxer/BoxesTest.java

@@ -17,6 +17,10 @@ package androidx.media3.muxer;
 
 import static androidx.media3.muxer.Mp4Muxer.LAST_FRAME_DURATION_BEHAVIOR_DUPLICATE_PREV_DURATION;
 import static androidx.media3.muxer.Mp4Muxer.LAST_FRAME_DURATION_BEHAVIOR_INSERT_SHORT_FRAME;
+import static androidx.media3.muxer.MuxerTestUtil.FAKE_AUDIO_FORMAT;
+import static androidx.media3.muxer.MuxerTestUtil.FAKE_CSD_0;
+import static androidx.media3.muxer.MuxerTestUtil.FAKE_CSD_1;
+import static androidx.media3.muxer.MuxerTestUtil.FAKE_VIDEO_FORMAT;
 import static androidx.media3.muxer.MuxerTestUtil.getExpectedDumpFilePath;
 import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.assertThrows;
@@ -57,15 +61,13 @@ public class BoxesTest {
 
   @Test
   public void createTkhdBox_forVideoTrack_matchesExpected() throws IOException {
-    Format videoFormat = MuxerTestUtil.getFakeVideoFormat();
-
     ByteBuffer tkhdBox =
         Boxes.tkhd(
             /* trackId= */ 1,
             /* trackDurationVu= */ 5_000_000,
             /* modificationTimestampSeconds= */ 1_000_000_000,
             /* orientation= */ 90,
-            videoFormat);
+            FAKE_VIDEO_FORMAT);
 
     DumpableMp4Box dumpableBox = new DumpableMp4Box(tkhdBox);
     DumpFileAsserts.assertOutput(
@@ -74,15 +76,13 @@ public class BoxesTest {
 
   @Test
   public void createTkhdBox_forAudioTrack_matchesExpected() throws IOException {
-    Format audioFormat = MuxerTestUtil.getFakeAudioFormat();
-
     ByteBuffer tkhdBox =
         Boxes.tkhd(
             /* trackId= */ 1,
             /* trackDurationVu= */ 5_000_000,
             /* modificationTimestampSeconds= */ 1_000_000_000,
             /* orientation= */ 90,
-            audioFormat);
+            FAKE_AUDIO_FORMAT);
 
     DumpableMp4Box dumpableBox = new DumpableMp4Box(tkhdBox);
     DumpFileAsserts.assertOutput(
@@ -315,11 +315,7 @@ public class BoxesTest {
             .setMaxInputSize(39)
             .setFrameRate(25)
             .setHeight(12)
-            .setInitializationData(
+            .setInitializationData(ImmutableList.of(FAKE_CSD_0, FAKE_CSD_1))
-                ImmutableList.of(
-                    BaseEncoding.base16()
-                        .decode("0000000167F4000A919B2BF3CB3640000003004000000C83C4896580"),
-                    BaseEncoding.base16().decode("0000000168EBE3C448")))
             .build();
 
     ByteBuffer videoSampleEntryBox = Boxes.videoSampleEntry(format);

libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerEndToEndTest.java

@@ -15,12 +15,11 @@
  */
 package androidx.media3.muxer;
 
+import static androidx.media3.muxer.MuxerTestUtil.FAKE_VIDEO_FORMAT;
 import static com.google.common.truth.Truth.assertThat;
 
-import android.content.Context;
 import android.media.MediaCodec.BufferInfo;
 import android.util.Pair;
-import androidx.media3.common.Format;
 import androidx.media3.extractor.mp4.Mp4Extractor;
 import androidx.media3.muxer.Mp4Muxer.TrackToken;
 import androidx.media3.test.utils.DumpFileAsserts;
@@ -31,7 +30,6 @@ import androidx.test.ext.junit.runners.AndroidJUnit4;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
-import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
@@ -42,24 +40,13 @@ import org.junit.runner.RunWith;
 public class Mp4MuxerEndToEndTest {
   @Rule public final TemporaryFolder temporaryFolder = new TemporaryFolder();
 
-  private Format format;
-  private String outputFilePath;
-  private FileOutputStream outputFileStream;
-
-  @Before
-  public void setUp() throws IOException {
-    outputFilePath = temporaryFolder.newFile("output.mp4").getPath();
-    outputFileStream = new FileOutputStream(outputFilePath);
-
-    format = MuxerTestUtil.getFakeVideoFormat();
-  }
-
   @Test
   public void createMp4File_addTrackAndMetadataButNoSamples_createsEmptyFile() throws IOException {
-    Mp4Muxer mp4Muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer mp4Muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
-      mp4Muxer.addTrack(/* sortKey= */ 0, format);
+      mp4Muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       mp4Muxer.setOrientation(90);
       mp4Muxer.addMetadata("key", "value");
     } finally {
@@ -72,8 +59,8 @@ public class Mp4MuxerEndToEndTest {
 
   @Test
   public void createMp4File_withSameTracksOffset_matchesExpected() throws IOException {
-    Context context = ApplicationProvider.getApplicationContext();
+    String outputFilePath = temporaryFolder.newFile().getPath();
-    Mp4Muxer mp4Muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    Mp4Muxer mp4Muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
     mp4Muxer.setModificationTime(/* timestampMs= */ 500_000_000L);
 
     Pair<ByteBuffer, BufferInfo> track1Sample1 =
@@ -87,12 +74,12 @@ public class Mp4MuxerEndToEndTest {
         MuxerTestUtil.getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 300L);
 
     try {
-      TrackToken track1 = mp4Muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken track1 = mp4Muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track1, track1Sample1.first, track1Sample1.second);
       mp4Muxer.writeSampleData(track1, track1Sample2.first, track1Sample2.second);
 
       // Add same track again but with different samples.
-      TrackToken track2 = mp4Muxer.addTrack(/* sortKey= */ 1, format);
+      TrackToken track2 = mp4Muxer.addTrack(/* sortKey= */ 1, FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track2, track2Sample1.first, track2Sample1.second);
       mp4Muxer.writeSampleData(track2, track2Sample2.first, track2Sample2.second);
     } finally {
@@ -107,15 +94,15 @@ public class Mp4MuxerEndToEndTest {
     FakeExtractorOutput fakeExtractorOutput =
         TestUtil.extractAllSamplesFromFilePath(new Mp4Extractor(), outputFilePath);
     DumpFileAsserts.assertOutput(
-        context,
+        ApplicationProvider.getApplicationContext(),
         fakeExtractorOutput,
         MuxerTestUtil.getExpectedDumpFilePath("mp4_with_same_tracks_offset.mp4"));
   }
 
   @Test
   public void createMp4File_withDifferentTracksOffset_matchesExpected() throws IOException {
-    Context context = ApplicationProvider.getApplicationContext();
+    String outputFilePath = temporaryFolder.newFile().getPath();
-    Mp4Muxer mp4Muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    Mp4Muxer mp4Muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
     mp4Muxer.setModificationTime(/* timestampMs= */ 500_000_000L);
 
     Pair<ByteBuffer, BufferInfo> track1Sample1 =
@@ -129,12 +116,12 @@ public class Mp4MuxerEndToEndTest {
         MuxerTestUtil.getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 200L);
 
     try {
-      TrackToken track1 = mp4Muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken track1 = mp4Muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track1, track1Sample1.first, track1Sample1.second);
       mp4Muxer.writeSampleData(track1, track1Sample2.first, track1Sample2.second);
 
       // Add same track again but with different samples.
-      TrackToken track2 = mp4Muxer.addTrack(/* sortKey= */ 1, format);
+      TrackToken track2 = mp4Muxer.addTrack(/* sortKey= */ 1, FAKE_VIDEO_FORMAT);
       mp4Muxer.writeSampleData(track2, track2Sample1.first, track2Sample1.second);
       mp4Muxer.writeSampleData(track2, track2Sample2.first, track2Sample2.second);
     } finally {
@@ -145,7 +132,7 @@ public class Mp4MuxerEndToEndTest {
     FakeExtractorOutput fakeExtractorOutput =
         TestUtil.extractAllSamplesFromFilePath(new Mp4Extractor(), outputFilePath);
     DumpFileAsserts.assertOutput(
-        context,
+        ApplicationProvider.getApplicationContext(),
         fakeExtractorOutput,
         MuxerTestUtil.getExpectedDumpFilePath("mp4_with_different_tracks_offset.mp4"));
   }

libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java

@@ -15,10 +15,11 @@
  */
 package androidx.media3.muxer;
 
+import static androidx.media3.muxer.MuxerTestUtil.FAKE_VIDEO_FORMAT;
+
 import android.content.Context;
 import android.media.MediaCodec.BufferInfo;
 import android.util.Pair;
-import androidx.media3.common.Format;
 import androidx.media3.extractor.mp4.Mp4Extractor;
 import androidx.media3.muxer.Mp4Muxer.TrackToken;
 import androidx.media3.test.utils.DumpFileAsserts;
@@ -29,7 +30,6 @@ import androidx.test.core.app.ApplicationProvider;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import java.io.FileOutputStream;
 import java.nio.ByteBuffer;
-import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
@@ -43,30 +43,18 @@ public class Mp4MuxerMetadataTest {
   // Input files.
   private static final String XMP_SAMPLE_DATA = "media/xmp/sample_datetime_xmp.xmp";
 
-  private Context context;
+  private final Context context = ApplicationProvider.getApplicationContext();
-  private String outputFilePath;
+  private final Pair<ByteBuffer, BufferInfo> sampleAndSampleInfo =
-  private FileOutputStream outputFileStream;
+      MuxerTestUtil.getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 0L);
-  private Format format;
-  private Pair<ByteBuffer, BufferInfo> sampleAndSampleInfo;
-
-  @Before
-  public void setUp() throws Exception {
-    context = ApplicationProvider.getApplicationContext();
-
-    outputFilePath = temporaryFolder.newFile("output.mp4").getPath();
-    outputFileStream = new FileOutputStream(outputFilePath);
-
-    format = MuxerTestUtil.getFakeVideoFormat();
-    sampleAndSampleInfo = MuxerTestUtil.getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 0L);
-  }
 
   @Test
   public void writeMp4File_orientationNotSet_setsOrientationTo0() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
@@ -83,11 +71,12 @@ public class Mp4MuxerMetadataTest {
 
   @Test
   public void writeMp4File_setOrientationTo90_setsOrientationTo90() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
 
       muxer.setOrientation(90);
@@ -106,11 +95,12 @@ public class Mp4MuxerMetadataTest {
 
   @Test
   public void writeMp4File_setOrientationTo180_setsOrientationTo180() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
 
       muxer.setOrientation(180);
@@ -129,11 +119,12 @@ public class Mp4MuxerMetadataTest {
 
   @Test
   public void writeMp4File_setOrientationTo270_setsOrientationTo270() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
 
       muxer.setOrientation(270);
@@ -152,11 +143,12 @@ public class Mp4MuxerMetadataTest {
 
   @Test
   public void writeMp4File_setLocation_setsSameLocation() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
       muxer.setLocation(33.0f, -120f);
     } finally {
@@ -174,11 +166,12 @@ public class Mp4MuxerMetadataTest {
 
   @Test
   public void writeMp4File_locationNotSet_setsLocationToNull() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
@@ -195,12 +188,13 @@ public class Mp4MuxerMetadataTest {
 
   @Test
   public void writeMp4File_setFrameRate_setsSameFrameRate() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
       muxer.setCaptureFps(120.0f);
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
@@ -217,12 +211,13 @@ public class Mp4MuxerMetadataTest {
 
   @Test
   public void writeMp4File_addStringMetadata_matchesExpected() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
       muxer.addMetadata("SomeStringKey", "Some Random String");
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
@@ -239,12 +234,13 @@ public class Mp4MuxerMetadataTest {
 
   @Test
   public void writeMp4File_addFloatMetadata_matchesExpected() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
       muxer.addMetadata("SomeStringKey", 10.0f);
-      TrackToken token = muxer.addTrack(/* sortKey= */ 0, format);
+      TrackToken token = muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();
@@ -261,7 +257,8 @@ public class Mp4MuxerMetadataTest {
 
   @Test
   public void writeMp4File_addXmp_matchesExpected() throws Exception {
-    Mp4Muxer muxer = new Mp4Muxer.Builder(outputFileStream).build();
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
 
     try {
       muxer.setModificationTime(/* timestampMs= */ 5_000_000L);
@@ -270,7 +267,7 @@ public class Mp4MuxerMetadataTest {
       ByteBuffer xmp = ByteBuffer.wrap(xmpBytes);
       muxer.addXmp(xmp);
       xmp.rewind();
-      TrackToken token = muxer.addTrack(0, format);
+      TrackToken token = muxer.addTrack(0, FAKE_VIDEO_FORMAT);
       muxer.writeSampleData(token, sampleAndSampleInfo.first, sampleAndSampleInfo.second);
     } finally {
       muxer.close();

libraries/muxer/src/test/java/androidx/media3/muxer/MuxerTestUtil.java

@@ -15,6 +15,9 @@
  */
 package androidx.media3.muxer;
 
+import static androidx.media3.common.MimeTypes.AUDIO_AAC;
+import static androidx.media3.common.MimeTypes.VIDEO_H264;
+
 import android.media.MediaCodec;
 import android.media.MediaCodec.BufferInfo;
 import android.util.Pair;
@@ -25,9 +28,24 @@ import java.nio.ByteBuffer;
 
 /** Utilities for muxer test cases. */
 /* package */ class MuxerTestUtil {
-  private static final byte[] FAKE_CSD_0 =
+
+  public static final byte[] FAKE_CSD_0 =
       BaseEncoding.base16().decode("0000000167F4000A919B2BF3CB3640000003004000000C83C4896580");
-  private static final byte[] FAKE_CSD_1 = BaseEncoding.base16().decode("0000000168EBE3C448");
+  public static final byte[] FAKE_CSD_1 = BaseEncoding.base16().decode("0000000168EBE3C448");
+  public static final Format FAKE_AUDIO_FORMAT =
+      new Format.Builder()
+          .setSampleMimeType(AUDIO_AAC)
+          .setSampleRate(40000)
+          .setChannelCount(2)
+          .build();
+  public static final Format FAKE_VIDEO_FORMAT =
+      new Format.Builder()
+          .setSampleMimeType(VIDEO_H264)
+          .setWidth(12)
+          .setHeight(10)
+          .setInitializationData(ImmutableList.of(FAKE_CSD_0, FAKE_CSD_1))
+          .build();
+
   private static final byte[] FAKE_H264_SAMPLE =
       BaseEncoding.base16()
           .decode(
@@ -40,23 +58,6 @@ import java.nio.ByteBuffer;
     return DUMP_FILE_OUTPUT_DIRECTORY + '/' + originalFileName + '.' + DUMP_FILE_EXTENSION;
   }
 
-  public static Format getFakeVideoFormat() {
-    return new Format.Builder()
-        .setSampleMimeType("video/avc")
-        .setWidth(12)
-        .setHeight(10)
-        .setInitializationData(ImmutableList.of(FAKE_CSD_0, FAKE_CSD_1))
-        .build();
-  }
-
-  public static Format getFakeAudioFormat() {
-    return new Format.Builder()
-        .setSampleMimeType("audio/mp4a-latm")
-        .setSampleRate(40000)
-        .setChannelCount(2)
-        .build();
-  }
-
   public static Pair<ByteBuffer, BufferInfo> getFakeSampleAndSampleInfo(long presentationTimeUs) {
     ByteBuffer sampleDirectBuffer = ByteBuffer.allocateDirect(FAKE_H264_SAMPLE.length);
     sampleDirectBuffer.put(FAKE_H264_SAMPLE);

libraries/transformer/src/test/java/androidx/media3/transformer/MuxerWrapperTest.java

@@ -15,6 +15,7 @@
  */
 package androidx.media3.transformer;
 
+import static androidx.media3.common.MimeTypes.AUDIO_AAC;
 import static androidx.media3.common.MimeTypes.VIDEO_H264;
 import static androidx.media3.transformer.MuxerWrapper.MUXER_MODE_MUX_PARTIAL_VIDEO;
 import static com.google.common.truth.Truth.assertThat;
@@ -25,9 +26,7 @@ import androidx.media3.common.ColorInfo;
 import androidx.media3.common.Format;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import com.google.common.collect.ImmutableList;
-import java.io.IOException;
 import java.nio.ByteBuffer;
-import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
@@ -36,8 +35,6 @@ import org.junit.runner.RunWith;
 /** Unit tests for {@link MuxerWrapper}. */
 @RunWith(AndroidJUnit4.class)
 public class MuxerWrapperTest {
-  @Rule public final TemporaryFolder temporaryFolder = new TemporaryFolder();
-
   private static final Format FAKE_VIDEO_TRACK_FORMAT =
       new Format.Builder()
           .setSampleMimeType(VIDEO_H264)
@@ -48,25 +45,20 @@ public class MuxerWrapperTest {
           .build();
   private static final Format FAKE_AUDIO_TRACK_FORMAT =
       new Format.Builder()
-          .setSampleMimeType("audio/mp4a-latm")
+          .setSampleMimeType(AUDIO_AAC)
           .setSampleRate(40000)
           .setChannelCount(2)
           .build();
 
   private static final ByteBuffer FAKE_SAMPLE = ByteBuffer.wrap(new byte[] {1, 2, 3, 4});
 
-  private String outputFilePath;
+  @Rule public final TemporaryFolder temporaryFolder = new TemporaryFolder();
-
-  @Before
-  public void setUp() throws IOException {
-    outputFilePath = temporaryFolder.newFile("output.mp4").getPath();
-  }
 
   @Test
-  public void changeToAppendVideoMode_afterDefaultMode_throws() {
+  public void changeToAppendVideoMode_afterDefaultMode_throws() throws Exception {
     MuxerWrapper muxerWrapper =
         new MuxerWrapper(
-            outputFilePath,
+            temporaryFolder.newFile().getPath(),
             new DefaultMuxer.Factory(),
             new NoOpMuxerListenerImpl(),
             MuxerWrapper.MUXER_MODE_DEFAULT);
@@ -75,10 +67,10 @@ public class MuxerWrapperTest {
   }
 
   @Test
-  public void setTrackCount_toTwoInMuxPartialVideoMode_throws() {
+  public void setTrackCount_toTwoInMuxPartialVideoMode_throws() throws Exception {
     MuxerWrapper muxerWrapper =
         new MuxerWrapper(
-            outputFilePath,
+            temporaryFolder.newFile().getPath(),
             new DefaultMuxer.Factory(),
             new NoOpMuxerListenerImpl(),
             MUXER_MODE_MUX_PARTIAL_VIDEO);
@@ -90,7 +82,7 @@ public class MuxerWrapperTest {
   public void setTrackCount_toTwoInAppendVideoMode_throws() throws Exception {
     MuxerWrapper muxerWrapper =
         new MuxerWrapper(
-            outputFilePath,
+            temporaryFolder.newFile().getPath(),
             new DefaultMuxer.Factory(),
             new NoOpMuxerListenerImpl(),
             MUXER_MODE_MUX_PARTIAL_VIDEO);
@@ -105,10 +97,10 @@ public class MuxerWrapperTest {
   }
 
   @Test
-  public void addTrackFormat_withAudioFormatInMuxPartialVideoMode_throws() {
+  public void addTrackFormat_withAudioFormatInMuxPartialVideoMode_throws() throws Exception {
     MuxerWrapper muxerWrapper =
         new MuxerWrapper(
-            outputFilePath,
+            temporaryFolder.newFile().getPath(),
             new DefaultMuxer.Factory(),
             new NoOpMuxerListenerImpl(),
             MUXER_MODE_MUX_PARTIAL_VIDEO);
@@ -122,7 +114,7 @@ public class MuxerWrapperTest {
   public void addTrackFormat_withSameVideoFormatInAppendVideoMode_doesNotThrow() throws Exception {
     MuxerWrapper muxerWrapper =
         new MuxerWrapper(
-            outputFilePath,
+            temporaryFolder.newFile().getPath(),
             new DefaultMuxer.Factory(),
             new NoOpMuxerListenerImpl(),
             MUXER_MODE_MUX_PARTIAL_VIDEO);
@@ -141,7 +133,7 @@ public class MuxerWrapperTest {
   public void addTrackFormat_withDifferentVideoFormatInAppendVideoMode_throws() throws Exception {
     MuxerWrapper muxerWrapper =
         new MuxerWrapper(
-            outputFilePath,
+            temporaryFolder.newFile().getPath(),
             new DefaultMuxer.Factory(),
             new NoOpMuxerListenerImpl(),
             MUXER_MODE_MUX_PARTIAL_VIDEO);
@@ -162,7 +154,7 @@ public class MuxerWrapperTest {
   public void isEnded_afterPartialVideoMuxed_returnsTrue() throws Exception {
     MuxerWrapper muxerWrapper =
         new MuxerWrapper(
-            outputFilePath,
+            temporaryFolder.newFile().getPath(),
             new DefaultMuxer.Factory(),
             new NoOpMuxerListenerImpl(),
             MUXER_MODE_MUX_PARTIAL_VIDEO);
@@ -179,7 +171,7 @@ public class MuxerWrapperTest {
   public void isEnded_afterStartingAppendVideo_returnsFalse() throws Exception {
     MuxerWrapper muxerWrapper =
         new MuxerWrapper(
-            outputFilePath,
+            temporaryFolder.newFile().getPath(),
             new DefaultMuxer.Factory(),
             new NoOpMuxerListenerImpl(),
             MUXER_MODE_MUX_PARTIAL_VIDEO);