diff --git a/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java b/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java
index eb4213bb9e..82f0164dc7 100644
--- a/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java
+++ b/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerMetadataTest.java
@@ -228,14 +228,12 @@ public class Mp4MuxerMetadataTest {
       muxer.close();
     }
 
-    // TODO(b/270956881): Use FakeExtractorOutput once it starts dumping custom metadata from the
-    //  meta box.
-    DumpableMp4Box dumpableBox =
-        new DumpableMp4Box(ByteBuffer.wrap(TestUtil.getByteArrayFromFilePath(outputFilePath)));
-    // The meta box should be present in the output MP4.
+    FakeExtractorOutput fakeExtractorOutput =
+        TestUtil.extractAllSamplesFromFilePath(new Mp4Extractor(), outputFilePath);
+    // Added string metadata should be present in the track metadata dump.
     DumpFileAsserts.assertOutput(
         context,
-        dumpableBox,
+        fakeExtractorOutput,
         MuxerTestUtil.getExpectedDumpFilePath("mp4_with_string_metadata.mp4"));
   }
 
@@ -252,13 +250,13 @@ public class Mp4MuxerMetadataTest {
       muxer.close();
     }
 
-    // TODO(b/270956881): Use FakeExtractorOutput once it starts dumping custom metadata from the
-    //  meta box.
-    DumpableMp4Box dumpableBox =
-        new DumpableMp4Box(ByteBuffer.wrap(TestUtil.getByteArrayFromFilePath(outputFilePath)));
-    // The meta box should be present in the output MP4.
+    FakeExtractorOutput fakeExtractorOutput =
+        TestUtil.extractAllSamplesFromFilePath(new Mp4Extractor(), outputFilePath);
+    // Added float metadata should be present in the track metadata dump.
     DumpFileAsserts.assertOutput(
-        context, dumpableBox, MuxerTestUtil.getExpectedDumpFilePath("mp4_with_float_metadata.mp4"));
+        context,
+        fakeExtractorOutput,
+        MuxerTestUtil.getExpectedDumpFilePath("mp4_with_float_metadata.mp4"));
   }
 
   @Test
@@ -278,7 +276,7 @@ public class Mp4MuxerMetadataTest {
       muxer.close();
     }
 
-    // TODO(b/270956881): Use FakeExtractorOutput once it starts dumping uuid box.
+    // TODO: b/288544833 - Use FakeExtractorOutput once it starts dumping uuid box.
     DumpableMp4Box dumpableBox =
         new DumpableMp4Box(ByteBuffer.wrap(TestUtil.getByteArrayFromFilePath(outputFilePath)));
     // The uuid box should be present in the output MP4.
diff --git a/libraries/test_data/src/test/assets/muxerdumps/mp4_with_float_metadata.mp4.dump b/libraries/test_data/src/test/assets/muxerdumps/mp4_with_float_metadata.mp4.dump
index 2f33ed2ca9..9fc305670e 100644
--- a/libraries/test_data/src/test/assets/muxerdumps/mp4_with_float_metadata.mp4.dump
+++ b/libraries/test_data/src/test/assets/muxerdumps/mp4_with_float_metadata.mp4.dump
@@ -1,40 +1,32 @@
-ftyp (28 bytes):
-  Data = length 20, hash EF896440
-mdat (71 bytes):
-  Data = length 55, hash 6B19F4A7
-moov (772 bytes):
-  mvhd (108 bytes):
-    Data = length 100, hash A5ADE288
-  meta (114 bytes):
-    hdlr (33 bytes):
-      Data = length 25, hash C39D0F5B
-    keys (37 bytes):
-      Data = length 29, hash 45F2DCDF
-    ilst (36 bytes):
-      Data = length 28, hash 2BFD5C32
-  trak (542 bytes):
-    tkhd (92 bytes):
-      Data = length 84, hash 8893F5BB
-    mdia (442 bytes):
-      mdhd (32 bytes):
-        Data = length 24, hash 50217AD
-      hdlr (44 bytes):
-        Data = length 36, hash A0852FF2
-      minf (358 bytes):
-        vmhd (20 bytes):
-          Data = length 12, hash EE830681
-        dinf (36 bytes):
-          Data = length 28, hash D535436B
-        stbl (294 bytes):
-          stsd (166 bytes):
-            Data = length 158, hash 11532063
-          stts (24 bytes):
-            Data = length 16, hash E4FC6483
-          stsz (24 bytes):
-            Data = length 16, hash 50B7F5B9
-          stsc (28 bytes):
-            Data = length 20, hash 8F6E8285
-          co64 (24 bytes):
-            Data = length 16, hash E4EE4D2E
-          stss (20 bytes):
-            Data = length 12, hash EE911E03
+seekMap:
+  isSeekable = true
+  duration = 0
+  getPosition(0) = [[timeUs=0, position=44]]
+  getPosition(1) = [[timeUs=0, position=44]]
+  getPosition(0) = [[timeUs=0, position=44]]
+  getPosition(0) = [[timeUs=0, position=44]]
+numberOfTracks = 1
+track 0:
+  total output bytes = 55
+  sample count = 1
+  format 0:
+    id = 1
+    sampleMimeType = video/avc
+    codecs = avc1.F4000A
+    maxInputSize = 85
+    width = 12
+    height = 10
+    colorInfo:
+      colorSpace = -1
+      colorRange = 1
+      colorTransfer = -1
+      hdrStaticInfo = length 0, hash 0
+    metadata = entries=[mdta: key=SomeStringKey, value=10.0, Mp4Timestamp: creation time=2082849800, modification time=2082849800, timescale=10000]
+    initializationData:
+      data = length 28, hash 410B510
+      data = length 9, hash FBADD682
+  sample 0:
+    time = 0
+    flags = 536870913
+    data = length 55, hash A481CEF4
+tracksEnded = true
diff --git a/libraries/test_data/src/test/assets/muxerdumps/mp4_with_string_metadata.mp4.dump b/libraries/test_data/src/test/assets/muxerdumps/mp4_with_string_metadata.mp4.dump
index db47e2afb5..bb71d4d3bd 100644
--- a/libraries/test_data/src/test/assets/muxerdumps/mp4_with_string_metadata.mp4.dump
+++ b/libraries/test_data/src/test/assets/muxerdumps/mp4_with_string_metadata.mp4.dump
@@ -1,40 +1,32 @@
-ftyp (28 bytes):
-  Data = length 20, hash EF896440
-mdat (71 bytes):
-  Data = length 55, hash 6B19F4A7
-moov (786 bytes):
-  mvhd (108 bytes):
-    Data = length 100, hash A5ADE288
-  meta (128 bytes):
-    hdlr (33 bytes):
-      Data = length 25, hash C39D0F5B
-    keys (37 bytes):
-      Data = length 29, hash 45F2DCDF
-    ilst (50 bytes):
-      Data = length 42, hash F4AA183B
-  trak (542 bytes):
-    tkhd (92 bytes):
-      Data = length 84, hash 8893F5BB
-    mdia (442 bytes):
-      mdhd (32 bytes):
-        Data = length 24, hash 50217AD
-      hdlr (44 bytes):
-        Data = length 36, hash A0852FF2
-      minf (358 bytes):
-        vmhd (20 bytes):
-          Data = length 12, hash EE830681
-        dinf (36 bytes):
-          Data = length 28, hash D535436B
-        stbl (294 bytes):
-          stsd (166 bytes):
-            Data = length 158, hash 11532063
-          stts (24 bytes):
-            Data = length 16, hash E4FC6483
-          stsz (24 bytes):
-            Data = length 16, hash 50B7F5B9
-          stsc (28 bytes):
-            Data = length 20, hash 8F6E8285
-          co64 (24 bytes):
-            Data = length 16, hash E4EE4D2E
-          stss (20 bytes):
-            Data = length 12, hash EE911E03
+seekMap:
+  isSeekable = true
+  duration = 0
+  getPosition(0) = [[timeUs=0, position=44]]
+  getPosition(1) = [[timeUs=0, position=44]]
+  getPosition(0) = [[timeUs=0, position=44]]
+  getPosition(0) = [[timeUs=0, position=44]]
+numberOfTracks = 1
+track 0:
+  total output bytes = 55
+  sample count = 1
+  format 0:
+    id = 1
+    sampleMimeType = video/avc
+    codecs = avc1.F4000A
+    maxInputSize = 85
+    width = 12
+    height = 10
+    colorInfo:
+      colorSpace = -1
+      colorRange = 1
+      colorTransfer = -1
+      hdrStaticInfo = length 0, hash 0
+    metadata = entries=[mdta: key=SomeStringKey, value=Some Random String, Mp4Timestamp: creation time=2082849800, modification time=2082849800, timescale=10000]
+    initializationData:
+      data = length 28, hash 410B510
+      data = length 9, hash FBADD682
+  sample 0:
+    time = 0
+    flags = 536870913
+    data = length 55, hash A481CEF4
+tracksEnded = true
diff --git a/libraries/transformer/src/test/java/androidx/media3/transformer/TransformerWithInAppMuxerEndToEndTest.java b/libraries/transformer/src/test/java/androidx/media3/transformer/TransformerWithInAppMuxerEndToEndTest.java
index dfd8d0b78d..8d73979570 100644
--- a/libraries/transformer/src/test/java/androidx/media3/transformer/TransformerWithInAppMuxerEndToEndTest.java
+++ b/libraries/transformer/src/test/java/androidx/media3/transformer/TransformerWithInAppMuxerEndToEndTest.java
@@ -104,7 +104,7 @@ public class TransformerWithInAppMuxerEndToEndTest {
     transformer.start(mediaItem, outputPath);
     ExportResult exportResult = TransformerTestRunner.runLooper(transformer);
 
-    // TODO(b/270956881): Use FakeExtractorOutput once it starts dumping uuid box.
+    // TODO: b/288544833 - Use FakeExtractorOutput once it starts dumping uuid box.
     assertThat(exportResult.exportException).isNull();
   }