Stream Opus/derived read path: serve from seekable disk FileStream, never a whole-file byte[]; HasOpusAsync is index-only

DeepDrftTests/TrackFormatDeliveryTests.cs

@@ -26,10 +26,10 @@ namespace DeepDrftTests;
 /// required to assert the delivery contract.
 ///
 /// The Range→206 contract is asserted at the load-bearing seam: ASP.NET performs the actual byte-slicing
-/// for any <see cref="FileResult"/> whose <see cref="FileResult"/>.EnableRangeProcessing is true. The lossless
-/// path proves this via the disk-stream <see cref="FileStreamResult"/>; the resolved Opus path via the
-/// in-memory <see cref="FileContentResult"/> — both must report range processing enabled, the explicit fix
-/// the 18.2 reviewer flagged for the byte[] path.
+/// for any <see cref="FileResult"/> whose <see cref="FileResult"/>.EnableRangeProcessing is true over a
+/// seekable stream. Both the lossless path AND the resolved Opus path now serve a disk-backed
+/// <see cref="FileStreamResult"/> (read-path streaming — no whole-file byte[]); both must report range
+/// processing enabled, and the FileStream is seekable, so an incoming Range yields a 206 slice.
 /// </summary>
 [TestFixture]
 public class TrackFormatDeliveryTests
@@ -59,13 +59,14 @@ public class TrackFormatDeliveryTests
 
         var result = await controller.GetTrack(entryKey, format: "opus");
 
-        var file = result as FileContentResult;
-        Assert.That(file, Is.Not.Null, "Opus delivery serves an in-memory byte[] (FileContentResult)");
+        var file = result as FileStreamResult;
+        Assert.That(file, Is.Not.Null, "Opus delivery streams from disk (FileStreamResult), not a byte[]");
+        var bytes = await ReadAllAsync(file!.FileStream);
         Assert.Multiple(() =>
         {
-            Assert.That(file!.ContentType, Is.EqualTo("audio/ogg"), "Opus bytes must carry the audio/ogg content-type");
-            Assert.That(file.FileContents, Is.EqualTo(OpusBytes), "The served bytes must be the Opus artifact, not the source");
-            Assert.That(file.EnableRangeProcessing, Is.True, "Range processing must be enabled on the resolved Opus byte[] path");
+            Assert.That(file.ContentType, Is.EqualTo("audio/ogg"), "Opus bytes must carry the audio/ogg content-type");
+            Assert.That(bytes, Is.EqualTo(OpusBytes), "The served bytes must be the Opus artifact, not the source");
+            Assert.That(file.EnableRangeProcessing, Is.True, "Range processing must be enabled on the resolved Opus stream path");
         });
     }
 
@@ -80,12 +81,13 @@ public class TrackFormatDeliveryTests
 
         var result = await controller.GetTrack(entryKey, format: "opus");
 
-        var file = result as FileContentResult;
-        Assert.That(file, Is.Not.Null, "The fallback still serves resolved bytes via the byte[] path");
+        var file = result as FileStreamResult;
+        Assert.That(file, Is.Not.Null, "The fallback still streams resolved bytes from disk (FileStreamResult)");
+        var bytes = await ReadAllAsync(file!.FileStream);
         Assert.Multiple(() =>
         {
-            Assert.That(file!.ContentType, Is.EqualTo("audio/wav"), "Fallback content-type must be the lossless source's MIME");
-            Assert.That(file.FileContents, Is.EqualTo(_sourceWav), "Fallback must serve the lossless source bytes");
+            Assert.That(file.ContentType, Is.EqualTo("audio/wav"), "Fallback content-type must be the lossless source's MIME");
+            Assert.That(bytes, Is.EqualTo(_sourceWav), "Fallback must serve the lossless source bytes");
             Assert.That(file.EnableRangeProcessing, Is.True, "Range processing stays enabled on the fallback path too");
         });
     }
@@ -167,6 +169,18 @@ public class TrackFormatDeliveryTests
 
     private byte[] _sourceWav = [];
 
+    // Drains a FileStreamResult's disk-backed stream to a byte[] and disposes it (read-path streaming serves
+    // an open FileStream, not a buffered byte[]). Disposing also releases the handle before temp-dir teardown.
+    private static async Task<byte[]> ReadAllAsync(Stream stream)
+    {
+        await using (stream)
+        {
+            using var ms = new MemoryStream();
+            await stream.CopyToAsync(ms);
+            return ms.ToArray();
+        }
+    }
+
     private async Task<FileDb> FreshDbAsync()
     {
         var db = await FileDb.FromAsync(_testDir);